this might be unrelated, but since I tried the xenial-proposed packages, the computer has crashed about once a day.  Usually I don't get any info on syslog, but I found this on syslog today:
Sep 30 13:32:28 xpc kernel: [19560.717703] INFO: task jbd2/dm-1-8:879 blocked for more than 120 seconds.
Sep 30 13:32:28 xpc kernel: [19560.717706]       Tainted: G           OE   4.4.0-38-generic #57-Ubuntu
Sep 30 13:32:28 xpc kernel: [19560.717706] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Sep 30 13:32:28 xpc kernel: [19560.717707] jbd2/dm-1-8     D ffff8800af107c98     0   879      2 0x00000000
Sep 30 13:32:28 xpc kernel: [19560.717710]  ffff8800af107c98 0000000000000246 ffff8801b8279b80 ffff8801b5d36040
Sep 30 13:32:28 xpc kernel: [19560.717712]  ffff8800af108000 ffff8800ae9718b8 ffff8800af107d88 ffff8800af107d70
Sep 30 13:32:28 xpc kernel: [19560.717713]  ffff8801b5d36040 ffff8800af107cb0 ffffffff8182c5f5 ffff8800ad776900
Sep 30 13:32:28 xpc kernel: [19560.717714] Call Trace:
Sep 30 13:32:28 xpc kernel: [19560.717720]  [<ffffffff8182c5f5>] schedule+0x35/0x80
Sep 30 13:32:28 xpc kernel: [19560.717723]  [<ffffffff812ebc40>] jbd2_journal_commit_transaction+0x240/0x1870
Sep 30 13:32:28 xpc kernel: [19560.717727]  [<ffffffff810c3d80>] ? wake_atomic_t_function+0x60/0x60
Sep 30 13:32:28 xpc kernel: [19560.717730]  [<ffffffff810ec93e>] ? try_to_del_timer_sync+0x5e/0x90
Sep 30 13:32:28 xpc kernel: [19560.717732]  [<ffffffff812f0e8a>] kjournald2+0xca/0x250
Sep 30 13:32:28 xpc kernel: [19560.717733]  [<ffffffff810c3d80>] ? wake_atomic_t_function+0x60/0x60
Sep 30 13:32:28 xpc kernel: [19560.717735]  [<ffffffff812f0dc0>] ? commit_timeout+0x10/0x10
Sep 30 13:32:28 xpc kernel: [19560.717736]  [<ffffffff810a08d8>] kthread+0xd8/0xf0
Sep 30 13:32:28 xpc kernel: [19560.717738]  [<ffffffff810a0800>] ? kthread_create_on_node+0x1e0/0x1e0
Sep 30 13:32:28 xpc kernel: [19560.717740]  [<ffffffff81830a8f>] ret_from_fork+0x3f/0x70
Sep 30 13:32:28 xpc kernel: [19560.717740]  [<ffffffff810a0800>] ? kthread_create_on_node+0x1e0/0x1e0
Sep 30 13:32:28 xpc kernel: [19560.717747] INFO: task vdr:1307 blocked for more than 120 seconds.
Sep 30 13:32:28 xpc kernel: [19560.717748]       Tainted: G           OE   4.4.0-38-generic #57-Ubuntu
Sep 30 13:32:28 xpc kernel: [19560.717748] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Sep 30 13:32:28 xpc kernel: [19560.717749] vdr             D ffff880198ac3b08     0  1307      1 0x00000004
Sep 30 13:32:28 xpc kernel: [19560.717750]  ffff880198ac3b08 ffff88017b477bc8 ffff8801b827a940 ffff8800aeeb0dc0
Sep 30 13:32:28 xpc kernel: [19560.717751]  ffff880198ac4000 ffff8800ae971870 00000000011d3628 ffff8800ae971870
Sep 30 13:32:28 xpc kernel: [19560.717753]  ffff8800ad776900 ffff880198ac3b20 ffffffff8182c5f5 ffff8800ae971800
Sep 30 13:32:28 xpc kernel: [19560.717754] Call Trace:
Sep 30 13:32:28 xpc kernel: [19560.717755]  [<ffffffff8182c5f5>] schedule+0x35/0x80
Sep 30 13:32:28 xpc kernel: [19560.717757]  [<ffffffff812e88da>] wait_transaction_locked+0x8a/0xd0
Sep 30 13:32:28 xpc kernel: [19560.717758]  [<ffffffff810c3d80>] ? wake_atomic_t_function+0x60/0x60
Sep 30 13:32:28 xpc kernel: [19560.717759]  [<ffffffff812e8b73>] add_transaction_credits+0x223/0x2a0
Sep 30 13:32:28 xpc kernel: [19560.717761]  [<ffffffff810c3ad5>] ? wake_up_bit+0x25/0x30
Sep 30 13:32:28 xpc kernel: [19560.717762]  [<ffffffff812e8d4c>] start_this_handle+0x10c/0x400
Sep 30 13:32:28 xpc kernel: [19560.717765]  [<ffffffff811ebe7a>] ? kmem_cache_alloc+0x1ca/0x1f0
Sep 30 13:32:28 xpc kernel: [19560.717766]  [<ffffffff812e923b>] jbd2__journal_start+0xdb/0x1e0
Sep 30 13:32:28 xpc kernel: [19560.717769]  [<ffffffff812a92dd>] ? ext4_rename+0x41d/0x900
Sep 30 13:32:28 xpc kernel: [19560.717771]  [<ffffffff812cd37d>] __ext4_journal_start_sb+0x6d/0x120
Sep 30 13:32:28 xpc kernel: [19560.717772]  [<ffffffff812a92dd>] ext4_rename+0x41d/0x900
Sep 30 13:32:28 xpc kernel: [19560.717774]  [<ffffffff81217cb4>] ? terminate_walk+0x64/0xd0
Sep 30 13:32:28 xpc kernel: [19560.717776]  [<ffffffff812a97dd>] ext4_rename2+0x1d/0x30
Sep 30 13:32:28 xpc kernel: [19560.717777]  [<ffffffff8121ad6c>] vfs_rename+0x58c/0x8e0
Sep 30 13:32:28 xpc kernel: [19560.717779]  [<ffffffff81344600>] ? security_kernel_fw_from_file+0x20/0x70
Sep 30 13:32:28 xpc kernel: [19560.717780]  [<ffffffff8121fbef>] SyS_rename+0x39f/0x3c0
Sep 30 13:32:28 xpc kernel: [19560.717782]  [<ffffffff818306f2>] entry_SYSCALL_64_fastpath+0x16/0x71
Sep 30 13:32:28 xpc kernel: [19560.717794] INFO: task kworker/u16:2:7411 blocked for more than 120 seconds.
Sep 30 13:32:28 xpc kernel: [19560.717795]       Tainted: G           OE   4.4.0-38-generic #57-Ubuntu
Sep 30 13:32:28 xpc kernel: [19560.717795] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Sep 30 13:32:28 xpc kernel: [19560.717796] kworker/u16:2   D ffff8801885777f8     0  7411      2 0x00000000
Sep 30 13:32:28 xpc kernel: [19560.717800] Workqueue: writeback wb_workfn (flush-252:1)
Sep 30 13:32:28 xpc kernel: [19560.717801]  ffff8801885777f8 00000000ffffffff ffff8801b8279b80 ffff8800940ee040
Sep 30 13:32:28 xpc kernel: [19560.717803]  ffff880188578000 ffff8800ae971870 00000000011d3628 ffff8800ae971870
Sep 30 13:32:28 xpc kernel: [19560.717804]  ffff8800ad776900 ffff880188577810 ffffffff8182c5f5 ffff8800ae971800
Sep 30 13:32:28 xpc kernel: [19560.717805] Call Trace:
Sep 30 13:32:28 xpc kernel: [19560.717806]  [<ffffffff8182c5f5>] schedule+0x35/0x80
Sep 30 13:32:28 xpc kernel: [19560.717808]  [<ffffffff812e88da>] wait_transaction_locked+0x8a/0xd0
Sep 30 13:32:28 xpc kernel: [19560.717809]  [<ffffffff810c3d80>] ? wake_atomic_t_function+0x60/0x60
Sep 30 13:32:28 xpc kernel: [19560.717810]  [<ffffffff812e8b73>] add_transaction_credits+0x223/0x2a0
Sep 30 13:32:28 xpc kernel: [19560.717811]  [<ffffffff812e8d4c>] start_this_handle+0x10c/0x400
Sep 30 13:32:28 xpc kernel: [19560.717813]  [<ffffffff810b6ebb>] ? dequeue_entity+0x41b/0xa80
Sep 30 13:32:28 xpc kernel: [19560.717814]  [<ffffffff811ebe7a>] ? kmem_cache_alloc+0x1ca/0x1f0
Sep 30 13:32:28 xpc kernel: [19560.717815]  [<ffffffff812e923b>] jbd2__journal_start+0xdb/0x1e0
Sep 30 13:32:28 xpc kernel: [19560.717816]  [<ffffffff8129d247>] ? ext4_writepages+0x3b7/0xcd0
Sep 30 13:32:28 xpc kernel: [19560.717818]  [<ffffffff812cd37d>] __ext4_journal_start_sb+0x6d/0x120
Sep 30 13:32:28 xpc kernel: [19560.717819]  [<ffffffff8129d247>] ext4_writepages+0x3b7/0xcd0
Sep 30 13:32:28 xpc kernel: [19560.717820]  [<ffffffff810ec834>] ? lock_timer_base.isra.22+0x54/0x70
Sep 30 13:32:28 xpc kernel: [19560.717822]  [<ffffffff810ec9b8>] ? del_timer_sync+0x48/0x50
Sep 30 13:32:28 xpc kernel: [19560.717823]  [<ffffffff8182f691>] ? schedule_timeout+0x131/0x270
Sep 30 13:32:28 xpc kernel: [19560.717825]  [<ffffffff810ec6b0>] ? trace_event_raw_event_tick_stop+0x120/0x120
Sep 30 13:32:28 xpc kernel: [19560.717827]  [<ffffffff810f5a8c>] ? ktime_get+0x3c/0xb0
Sep 30 13:32:28 xpc kernel: [19560.717830]  [<ffffffff8113e6d6>] ? delayacct_end+0x56/0x60
Sep 30 13:32:28 xpc kernel: [19560.717833]  [<ffffffff8119c21e>] do_writepages+0x1e/0x30
Sep 30 13:32:28 xpc kernel: [19560.717834]  [<ffffffff8123c1a5>] __writeback_single_inode+0x45/0x340
Sep 30 13:32:28 xpc kernel: [19560.717836]  [<ffffffff8123c9b2>] writeback_sb_inodes+0x262/0x600
Sep 30 13:32:28 xpc kernel: [19560.717837]  [<ffffffff8123cddc>] __writeback_inodes_wb+0x8c/0xc0
Sep 30 13:32:28 xpc kernel: [19560.717838]  [<ffffffff8123d133>] wb_writeback+0x253/0x310
Sep 30 13:32:28 xpc kernel: [19560.717841]  [<ffffffff81229c31>] ? get_nr_dirty_inodes+0x51/0x80
Sep 30 13:32:28 xpc kernel: [19560.717842]  [<ffffffff8123d9aa>] wb_workfn+0x2ea/0x400
Sep 30 13:32:28 xpc kernel: [19560.717844]  [<ffffffff8109a395>] process_one_work+0x165/0x480
Sep 30 13:32:28 xpc kernel: [19560.717845]  [<ffffffff8109a6fb>] worker_thread+0x4b/0x4c0
Sep 30 13:32:28 xpc kernel: [19560.717847]  [<ffffffff8109a6b0>] ? process_one_work+0x480/0x480
Sep 30 13:32:28 xpc kernel: [19560.717848]  [<ffffffff8109a6b0>] ? process_one_work+0x480/0x480
Sep 30 13:32:28 xpc kernel: [19560.717849]  [<ffffffff810a08d8>] kthread+0xd8/0xf0
Sep 30 13:32:28 xpc kernel: [19560.717850]  [<ffffffff810a0800>] ? kthread_create_on_node+0x1e0/0x1e0
Sep 30 13:32:28 xpc kernel: [19560.717851]  [<ffffffff81830a8f>] ret_from_fork+0x3f/0x70
Sep 30 13:32:28 xpc kernel: [19560.717852]  [<ffffffff810a0800>] ? kthread_create_on_node+0x1e0/0x1e0