I use it as a wireless hotspot to get work done on a laptop PC on a regular basis. Every other day or so, after a few hours of running smoothly, the hotspot service (or packet data) begins to misbehave. The buttons to enable/disable either stop responding.
When that happens, the only solution is to restart the device. This trend was there while running GingerBread, and it still is there now running Ice Cream Sandwich. I have learnt to live with it. As a matter of fact, I am writing this article because it just pulled that stunt on me a few minutes ago.
Oh, and I have had the Galaxy S II reset a couple of times while running the WordPress app for Android. Yes; life happens. It is all in the day of a mobile user.