I have succesfully imported AAF from Premiere only into Vegas 8. It’s extremely flaky, it imports all sequences from Premiere to one timeline in Vegas, but you can delete superfluous tracks and work right on. Both all audio and video with handles will be preserved.
It works. Getting Avid just for converting AAFs between Premiere and Protools is an overkill. And be aware that CS4 dropped AAF support altogether (although they promise to bring it back later as an update, as well as OMG support).