Comment 8 for bug 1437492

I don't have any old kernels around.
Yes, I believe this to be a regression, since I don't recall having this slow boot long time ago.

Interestingly GRUB to LightDM with systemd is 45 seconds.
While GRUB to LightDM with upstart is 10 seconds (then I have to wait about half a minute for the USB devices to get initialised)

$ lsusb
Bus 004 Device 002: ID 8087:8000 Intel Corp.
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 002: ID 8087:8008 Intel Corp.
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 002: ID 174c:3074 ASMedia Technology Inc.
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 006: ID 045e:0047 Microsoft Corp. IntelliMouse Explorer 3.0
Bus 001 Device 007: ID 046d:c313 Logitech, Inc. Internet 350 Keyboard
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

$ lsusb -s 1
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Since the slow delayed boot remained even after plugging out my USB keyboard and USB mouse, it seems the culprit is the internal USB hub on the Intel Z87 (Haswell) chipset.