Upgrade to 3.0

I am working with a project we are getting ready to release and now
wondering if we should start looking at upgrading to 3.0 beofre
releasing.

I was hoping to get some advice. Of course, upgrading something once
it is released is much harder than doing it prior to release. However,
I am not sure which gems/plugins are going to be compatibale without
bugs and what not.

Thoughts?