It depends.
If it is the most important use I make of the device, I'd say that a single app is a more than enough reason to hold back onto a previous OS.
Updating to the newest OS is not mandatory, and I'd say that a time of adjustment is rather physiological in every new iteration of any OS.
Think that, despite all tests the developers might have done, widespread use with the new OS are possible only after release (how many beta testers had access to the betas of iOS5?)
Now, just give us the fixes
s
(of course I'm sorry for the iPhone 4S users that don't have this choice…)