I spent 7 hours trying to upgrade to iOS 5 last night. Eventually, it worked and I have the new firmware, but it is a shame that it came at the cost of everything on my iPhone.
Despite having taken forever to make 2 backups last night, when the restore portion of the update process came to pass (at about 1am) it failed. It gave me an unhelpful message, so I went to manually find my backups. Both folders were still there, but they were empty.
My RSS and Twitter are full of similar stories, and, even worse, tales of bricks. The official (?) line is that the Apple verification and activation servers are struggling under the load. This is only going to get worse with the 4S being launched tomorrow. I really would leave it for a while, if you want to avoid the risk.
I am definitely not trusting my iPad to the process. Losing my phone's contents was annoying, and a time sink, but losing my iPad's contents would be disastrous.
Another note: if you activated gestures on iPad 1, which involved either a jailbreak or a Mac, that option will no longer exist on the iPad 1. I'm waiting for an untethered jailbreak and a hack for gestures on Cydia.