First, to the naysayers and bad reviews...this is not some simple install-and-go module with 2 or 3 settings and wham, you're done. But therein lies the real power of this component - once you learn your way around, you can do anything.
As far as the MIs being buggy, I had some trouble getting PayPal to work, but this was a "me and PayPal" issue, not the extension. I am going to suggest, or post myself, some of the PP troubleshooting that the author of this software provided me...I think it would be a big help to folks.
I have this integrated with DocMan and NOIX ACL, and it works like a charm. I have sections of the site blocked off, documents protected for subscribers, and an easy payment process. Upgrades and downgrades of subscriptions are easy using the MIs once you learn it, kicking the subscribers to different ACL or DocMan groups for access to different sections and documents.
It was not EASY, but with a little perseverance and thought, it's really an awesome solution for my purposes, and I would bet that with some help the CB integration and other problems on these reviews could be solved.
If you are a novice at this sort of thing, but really need a powerful solution for a pay web site with different types of content, I would definitely recommend getting a support plan, it will be well worth the small cost.
All I can say is that I am extremely happy with the decision I made to go with AEC, and if you are looking for a super solution and aren't scared of a bit of a learning curve, give it a shot - I think you will really like it.