I had used 2 Verizon iPhone's current iOS 4.2.10
After reading all the threads and posts for everyone having various issues i did the follow prep work prior to installing the new iOS.
I backed up my iphone first then ran a sync without music, photos, and video. I left apps alone since i did not have that much to begin with. I left my contacts on phone since I use exchange setup with Google anyway. Took 4 hours (UGH!!!) to download, but! updated both my wife's and my phone. No problems on restore. After the devices boot back you have to go through some questions on setup. Nice thing I noticed was that while going through setup the devices were syncing in background, no more sync in progress, you can actually use the device while syncing with iTunes. Good luck to everyone!!
The download process *****. I have wasted my weekend dealing with updating software on my Apple devices. Apple should make this a lot easier and fix the downloading problems first. I have had to restore three ipads, an itouch, and an iphone today, wasting hours of time. Next time I will send Apple a bill.
Apple makes a huge mistake by not making it clear HOW LONG this can take. The are so full of themselves at this point and are losing touch with their user base. They have come to believe that, if they think it,it must be true. Trust me, and this comes from an early adopter and long time Mac user, there are dark days ahead....