Upgrading to 3.0

We're in the final stages of a redesign using WPMU 2.9.2 and now it looks like 3.0 is coming out very soon. Do we wait and upgrade MU and all of our plugins or do we go with what we have been working on and upgrade down the road when the bugs are worked out?

This is our first upgrade (from an old version) so I am wondering just how complicated is it to upgrade an install that is using a lot of plugins?

Thanks,
Helen