Mine was working 100% fine up until dinner today. I put it in on the table and left it, and 5 minutes later it wouldn't turn on. Worked again after soft reset, got in the car, and it locked up again. At this point I reset it several times and it kept locking up again in under a minute. I reset it again when I got home, and plugged it in. At this point it stopped locking up, but was acting really sluggish/choppy. I turned it off and came back a few hours later, and it seems buttery smooth again.
My suspicion is this is related to the battery. I had been playing music on the phone all day, and keeping an eye on the battery - for several hours it stayed at 100% before it even started going down, and at the restaurant it was showing 68% before it locked up the first time. I bet it was actually running out of batteries and not getting enough power, but not shutting itself down due to thinking it was still full. I'll see tomorrow if it works during the day and starts to get flaky later in the day.
Edit: it could also be related to my cars Bluetooth on the drive back, but I doubt it since it hadn't locked up the night before or in the morning on my commute.