Mine and a co-workers experience with 4.2....
One of my coworkers upgraded and was having issues so we upgraded mine to see if we could replicate the problems....and we did.
By the end of the day we were both reverting back to 3.2.2.
We both started out ok, liked the folders and the multitasking. Didn't care one way or the other on the orientation/silent mode change. I always use the volume controls anyways and I never use the orientation lock. We both had issues where the Wifi would show "off" and you couldn't turn it on. You could flip it to "on" but it wouldn't stay. It would revert whenever you left that screen to "Off". Even in the "Off" state with no wireless connection showing, I was able to connect to a private network that is only accessible from the wireless network. So it was obviously still connected. However, when going to the network settings, it would tell me it couldn't join the network. I purchased WiFiFoFum before it was pulled from the APP store so i turned off 3G/CellularData and cranked up the APP. It was able to see all of the networks in the area, even though the WiFi was "Off". Usually the WiFi would behave again for a while after a reboot. As the day progressed, we had more issues where going to the general settings, you got a white screen for a long time, and it would either dump you at the home screen or you would have to exit out and shut it via multitasking. Near the end of the day, it would not connect to the internet via WiFi or 3G. Oddly this happened after trying to get it to see our network printer - happened on both ipads. Mine is a 64GB and his is a 32GB, both with WiFi and 3G.
Overall, I like the new OS. It is a Beta, so odd things are expected. Thats the purpose of the Beta. Once Apple gets the kinks worked out, I'll definitely give the next Beta a try. One BIG plus was that I was able to download and test the Juniper Networks Pulse client (ssl vpn). It did not show up when accessing the Itunes store via the Ipad, but I downloaded it via my PC from Itunes and added it to my Ipad via Itunes. The app is iphoneish (1x/2x) as far as display, but it works. I was able to connect to our SA2500 and connect to the network without any problems using my RSA keyfob.
I just don't relish waiting till November some time now that I've had a taste.....