KevinC,
Here's my take on the issue of 7th ed vs. 8th ed vs. 9th Age:
I'd like to have a game with any, if I only had the time. Thinking aloud...
The 7th ed AB was more balanced, whereas the 8th ed AB clearly made some units inferior and other (some completely new) units very powerful. This with the same edition ABs and BRBs. Simply, it felt bad playing with the army I had built for the 7th ed, and I didn't like the idea of a major modification just because GW put out new rules.
I think 7th ed AB with 8th ed BRB still had good interior balance, and played games with that combo. But the laser artillery and indirect clearly made Empire a bit too powerful, and warranted the direction that the 8th AB took (although it went too far with most black powder units). Still, there was too much of the "buy this nice centerpiece gadget" in the 8th edition. Just a little bit too much. And there was too much random magic.
As to the 9th Age Empire, I really like the way they handle the units, making all of them playable and bringing back some lost units and lost combat roles (Reiksguard on foot, Pistoliers charge!). It definitely is WHFB, simply because it has been built on that engine, and has all those characteristic units. No doubt about that.
Then again, the 8th ed introduced Horde and Supporting Attacks, neither of which I think make much sense. I see them as inferior game design that promotes bloodfests instead of tactics. I'd rather maneuver than just hack and slash. IIRC these rules are still in the 9th Age, and I'm hoping the good people would rethink them. (Correct me if I'm wrong, haven't read the rules for some months.)
All this said,
the 9th Age is definitely the new generally shared edition after the 8th, for me. Also partially because it seems to be the most played version around where I live (right after KoW). When I have the time, there will come games in the local club using this system. A test game with the 7th ed showed that I had somewhat romantic memories of how that edition plays, and indeed I like some of the gamey aspects of the 8th ed, and enjoy having them in the 9th Age.
Still, there's always hope for a WHFB game fitting to my vision (everyone has this, I guess). KoW plays differently, is a different game I like, but not a 1:1 substitute for any WHFB edition.
-Z