Did anybody have problems with migrating Xcode3.2x projects to Xcode4?

At the moment I'm in a production cycle with submitting updates to my App every 2 weeks in average. I'm thinking of migrating to Xcode4 right now. Did anybody have problems with migrating projects or archiving or submitting to store? If so, best practises in solving such issu开发者_如何学编程es are very welcome.

I haven't experienced any problems and the transition guide claims:

Working on a Project in Xcode 4 Leaves Your Xcode 3 Preferences Untouched

I've also read somewhere else (but can't find it) that Xcode 4 uses the Xcode 3 project format unchanged. So far I can confirm this.