Yes.
For beta 1, wow it's stable. There's of course occasional bugs but nothing too serious!
I have had some pretty obvious bugs in the beta so far:
- After going in and out of a few different conversations, the name of the person gets frozen. Upon opening a new conversation, they overlap, and so on. Eventually the conversation names are all just a black smudge of 10 different names. Have to restart the Messages app to fix this.
- Random shut downs of the whole iPhone, very annoying if you're for example.. playing a game and getting a high score

because this closes down all apps.
- Trouble from sleep wake, where the device doesn't wake for a minute or two. Annoying. This has happened when receiving calls. You can hear the ringer, you can't silence the call, and you can't pick it up. doesnt react to hardware silence switch either.
- Overlap of the clock and music buttons, upon double pressing the home button from sleep.
- Upon wake, sometimes the brightness of the device becomes the 'minimum brightness', even though the brightness is set to maximum (without automatic brightness selected). A screen lock and wake, usually resets this.
- About half the time, video recording doesn't work. Neither the record button nor the volume buttons initiate the video recording.
Just off the top of my head.
You would think Messages, going from sleep wake, double clicking the home button and video recording would have been THOROUGHLY tested by Apple within the first WEEK of testing, they work on these for months before the first beta comes out, its a huge overhaul, so how did they not fix it before the first beta was released
Anyway, considering all the changes they have done, its a huge effort. But i wouldn't call it stable, yet
