Hey Paul,
I have always been an E9 fan and even as a consultant did some cherry picking of clients for a long time with the express purpose of avoiding E10 (terrible i know) but I can honestly say I have come to find E10 to be comparable in nearly all areas (except Insight, which is just plain 100% different than E9 reporting) and in many ways easier. In terms of the power user functionality you can get to and do everything you are used to, in terms of teaching new users the learning curve is much less steep on E10 than it was with E9. I know the transition can be painful and we're helping clients do it still (rumor has it there are a small number of hold outs in the Eloqua universe these days) but once you make the transition it really isn't bad at all. I would argue the transition from another MAP tool to Eloqua is harder than E9 to E10 and that you'll find plenty of the UI improvements and daily functionality/productivity gains to be worth it! I'd be happy to give you my $0.02 anytime, feel free to DM me.
Best,
Lauren