Looking at my syslog at the exact minute that got stuck (time presented by the greeter), I wasn't really using the phone (it was trying to suspend), and I also noticed the GPS was reporting issues, not sure if related or not though:
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.707790][pm_notifier_call_chain]: there are 4 notify callbacks, event = 4
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.707853]msdc: 0,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.707918]msdc: 1,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.709977]PM: suspend exit 2015-02-03 20:27:08.594582999 UTC
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.710031]PM: suspend entry 2015-02-03 20:27:08.594646769 UTC
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.710042]PM: Syncing filesystems ... done.
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.747749][pm_notifier_call_chain]: there are 4 notify callbacks, event = 3
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.747780]Freezing user space processes ... [GPS] GPS_read: signaled by -ERESTARTSYS(-512) 
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.748746] 
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.748831]last active wakeup source: eventpoll
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.748843]
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.748856]Freezing of tasks aborted after 0.001 seconds (38 tasks refusing to freeze, wq_busy=0):
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.748870]
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.748876]Restarting tasks ... done.
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.757297][pm_notifier_call_chain]: there are 4 notify callbacks, event = 4
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.757363]msdc: 0,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.757431]msdc: 1,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.759542]PM: suspend exit 2015-02-03 20:27:08.644146461 UTC
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.759598]PM: suspend entry 2015-02-03 20:27:08.644212999 UTC
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.759609]PM: Syncing filesystems ... done.
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.802887][pm_notifier_call_chain]: there are 4 notify callbacks, event = 3
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.802918]Freezing user space processes ... [GPS] GPS_read: signaled by -ERESTARTSYS(-512) 
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.804001] 
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.804230]last active wakeup source: eventpoll
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.804243]
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.804256]Freezing of tasks aborted after 0.001 seconds (38 tasks refusing to freeze, wq_busy=0):
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.804270]
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.804276]Restarting tasks ... done.
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.811308][pm_notifier_call_chain]: there are 4 notify callbacks, event = 4
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.811369]msdc: 0,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.811433]msdc: 1,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.813211]PM: suspend exit 2015-02-03 20:27:08.697819076 UTC
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.813268]PM: suspend entry 2015-02-03 20:27:08.697882999 UTC
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.813279]PM: Syncing filesystems ... done.
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.865217][pm_notifier_call_chain]: there are 4 notify callbacks, event = 3
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.883886]Freezing user space processes ... 
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.884312]last active wakeup source: eventpoll
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.884324]
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.884337]Freezing of tasks aborted after 0.000 seconds (38 tasks refusing to freeze, wq_busy=0):
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.884351]
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.884358]Restarting tasks ... [GPS] GPS_read: signaled by -ERESTARTSYS(-512) 
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.885181] done.
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.885424][pm_notifier_call_chain]: there are 4 notify callbacks, event = 4
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.885458]msdc: 0,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.885473]msdc: 1,mmc_schedule_delayed_work ret= 1
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.903665]PM: suspend exit 2015-02-03 20:27:08.788265384 UTC
Feb  3 18:27:08 ubuntu-phablet kernel: [43408.903708]PM: suspend entry 2015-02-03 20:27:08.788323461 UTC
Feb  3 18:27:09 ubuntu-phablet kernel: [43408.903719]PM: Syncing filesystems ... done.
Feb  3 18:27:09 ubuntu-phablet kernel: [43408.916151][pm_notifier_call_chain]: there are 4 notify callbacks, event = 3
Feb  3 18:27:09 ubuntu-phablet kernel: [43408.916184]Freezing user space processes ... [GPS] GPS_read: signaled by -ERESTARTSYS(-512) 
Feb  3 18:27:09 ubuntu-phablet kernel: [43408.916793] (elapsed 0.001 seconds) done.
Feb  3 18:27:09 ubuntu-phablet kernel: [43408.917874]Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.