>We are going to upgrade our application from VFP 3.0 to VFP 7.0 (sorry, we will wait for version 8.0 until stability have been fully demonstrated :)

Really, you're the only one who can demonstrate the stability of your own application. You may have code in your app that tweaks a problem that nobody else does, or you may avoid a problem that everyone else is hitting. I'd recommend going right up to 8, and then downgrading if there's a problem: there's no benefit I can see in waiting.