I'm coming from a WRX, suspension, engine and electronics mods.
One thing about the WRX was, it was TOO much car. As in, I could head out to the hills, leave it at 4k RPMs in 4th, and never touch the brakes through the curves. So, short of pulling up to the 5-0 and just asking him to ticket me... it just wasn't that much of a challenge anymore. Not to mention the rough ride and worrying about my wheels all the time (low sidewalls + rough roads = nervous).
The Baja is, as a friend put it, a DEE-luxe machine. It's alot of car (and a little bit of truck). It feels much more refined and accomodating than the WRX.
I'd question getting one if you're still bugging for raw performance. Hook up with a WRX wagon (what I had) or a Forester XT if you're wanting to mod up etc. and take it autocrossing.
Like everybody else, I'm really curious about what the engine is or isn't. I'm not going to do any engine mods until my warranty goes bonk, but a bigger turbo, some plumbing, and I reckon the Baja's going to give some seriously nice cars fits off the line.
As it is, I never feel outgunned. It took me a long time to get good with the WRX, and if you're good with your WRX then you're going to be good with a Baja. I don't look for races, but I've definitely left some surprised quick cars behind. If you're in a stock WRX and aren't good with it, my Baja will say bye-bye for sure.
I've never experience the understeer everyone brings up, if anything I can bring the rear end around easier on the Baja than I could on the WRX. Stock, I'd say the suspension is freaking good. Like the WRX, the stock tires are cr*p.
To me, the Baja (turbo) is about getting over having a car that everybody knows is fast and trendy and a pain in the butt to keep clean (if you're using it to haul stuff like in a wagon), and getting into a car that you can throw nasty stuff in the back, be much more comfortable inside of, and still fling around more than Johnny Law would like you to. The Baja grows on me every day, while the WRX got to be more and more a drag to deal with.
Go drive one!