The symptoms I've got are bizarre. With my home router, things sometimes work great, and other times every site is painfully slow. pinging google.com shows some packet loss (~5%) and ridiculous latencies of about 4 seconds! Disconnecting and reconnecting sometimes fixes it. Using the production XPS 13 Developer Edition with stock software.

$ ping www.google.com
PING www.google.com (74.125.129.106) 56(84) bytes of data.
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=1 ttl=47 time=5180 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=2 ttl=47 time=5256 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=3 ttl=47 time=5352 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=4 ttl=47 time=4819 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=5 ttl=47 time=4906 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=6 ttl=47 time=4775 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=7 ttl=47 time=4309 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=8 ttl=47 time=4335 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=9 ttl=47 time=4475 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=11 ttl=47 time=4343 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=12 ttl=47 time=4455 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=13 ttl=47 time=4486 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=14 ttl=47 time=3486 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=15 ttl=47 time=4176 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=16 ttl=47 time=3417 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=17 ttl=47 time=2960 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=18 ttl=47 time=3394 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=19 ttl=47 time=3331 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=20 ttl=47 time=3897 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=21 ttl=47 time=3991 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=23 ttl=47 time=3989 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=24 ttl=47 time=3460 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=25 ttl=47 time=3579 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=26 ttl=47 time=4145 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=27 ttl=47 time=4189 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=28 ttl=47 time=4273 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=29 ttl=47 time=3959 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=30 ttl=47 time=3578 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=31 ttl=47 time=3672 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=32 ttl=47 time=3762 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=33 ttl=47 time=3278 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=34 ttl=47 time=3359 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=35 ttl=47 time=3660 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=36 ttl=47 time=4469 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=37 ttl=47 time=3969 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=38 ttl=47 time=4079 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=39 ttl=47 time=4164 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=40 ttl=47 time=3510 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=41 ttl=47 time=3275 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=42 ttl=47 time=3419 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=43 ttl=47 time=2922 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=44 ttl=47 time=3312 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=45 ttl=47 time=2974 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=46 ttl=47 time=3531 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=47 ttl=47 time=3321 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=48 ttl=47 time=3298 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=49 ttl=47 time=3110 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=50 ttl=47 time=3824 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=51 ttl=47 time=3913 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=52 ttl=47 time=3867 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=53 ttl=47 time=3979 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=54 ttl=47 time=4078 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=55 ttl=47 time=3794 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=56 ttl=47 time=3313 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=57 ttl=47 time=4714 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=58 ttl=47 time=3745 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=60 ttl=47 time=3883 ms

Then I disconnected & reconnected.

64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=72 ttl=47 time=16.5 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=73 ttl=47 time=20.0 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=74 ttl=47 time=24.9 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=75 ttl=47 time=16.8 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=76 ttl=47 time=17.5 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=77 ttl=47 time=24.1 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=78 ttl=47 time=37.2 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=79 ttl=47 time=24.8 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=80 ttl=47 time=29.4 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=81 ttl=47 time=65.4 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=82 ttl=47 time=97.4 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=83 ttl=47 time=137 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=84 ttl=47 time=81.1 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=85 ttl=47 time=98.8 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=86 ttl=47 time=183 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=87 ttl=47 time=97.8 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=88 ttl=47 time=206 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=89 ttl=47 time=115 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=90 ttl=47 time=34.9 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=91 ttl=47 time=27.5 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=92 ttl=47 time=57.5 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=93 ttl=47 time=19.5 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=94 ttl=47 time=23.7 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=95 ttl=47 time=20.2 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=96 ttl=47 time=17.5 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=97 ttl=47 time=26.1 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=98 ttl=47 time=17.1 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=99 ttl=47 time=37.2 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=100 ttl=47 time=52.6 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=101 ttl=47 time=82.3 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=102 ttl=47 time=126 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=103 ttl=47 time=64.8 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=104 ttl=47 time=72.9 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=105 ttl=47 time=75.4 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=106 ttl=47 time=28.6 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=107 ttl=47 time=23.7 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=108 ttl=47 time=26.5 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=109 ttl=47 time=34.8 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=110 ttl=47 time=29.0 ms
64 bytes from pd-in-f106.1e100.net (74.125.129.106): icmp_req=111 ttl=47 time=32.0 ms

When it's in the "good state" there is zero packet loss.