Funny but I just posted about this. Bottom line: if precision is important to you, either stay in AA1.5 or do the mix from scratch in AA3. For all intents and purposes they are different programs, and far more than the way the series/parallel effects work is at stake. Effects with the same settings end up not sounding the same between the two versions. That's my 2c. Sorry it's not so easy.
Sorry I missed your post. Thanks for the advice. It seems to me that there should have been more thought given to making 3.0 backward compatible with older sessions, if for no other reason than it would have kept users with Adobe. If you have to re-mix everything anyway it might be time to consider a different DAW but for now I'll keep 1.5 for the old stuff, 3.0 for the new.
G.