I did - if I had a 328/330, I would probably go the ESS route - it gives more gains than the AA charger (It would still be on the table for debate for me at least). The reason I'm going the AA route is because it's 'safer' on the engine, a little less psi (believe it's a measily 6-7) is being pushed, so it'd improve the 'longevity' of my cast engine with it bolted on. It's still my 'daily driver' for a little while, putting the SC in it may spell the end of it's daily driving days. The 'safer' part I mentioned may just be a figment of my imagination, but I've read alot in the FI forums here and there, and it's considered the simpler/easier/tad safer of the 2 (from the 323 cast engine perspective). Across the board, the ESS chargers do have higher gains - and higher psi levels being pushed.
Honestly if I get myself into a new E90 or 5 series - then this car will become my full time plaything, and I may just pull the engine in favor of the M 3.2, or a 330 3.0 and then slap on a bigger SC since they can take higher psi levels with the forged engines. I'd very likely go ESS in that respect - or call it a day with the 3.2 (I know - why not just sell the car and get what I want.. I guess I'm attached to it now, especially after putting time/money into it. And well, I already have it!)
ESS gets good reviews - I guess I've always leaned towards the AA's since I look at the car from a 'daily' driving perspective. (for now) There is also a tuning shop here in town that does good installs with AA chargers. A few of the local bimmer guys have slapped AA chargers in their cars, and not batted an eye afterwards (1 with a 330 with SC for 2 years, another with a 323 just got his AA put in a few months ago). So I know I have some good local support if things got flakey. (That was the other thought that kept going through my mind - I'm not a 'real' mechanic by any means. If the SC flakes, can I go local for work or is my car going out of state on a flatbed?)
The price is down on those ESS's too, 6k is less than I recall seeing it for previously. (awesome!) Hopefully the price on the SC's will continue to go down as the availability of these cars increases.