I've only played with it in a lab setup to date, so I can only base judgement on that. Performance was OK with AMD, but not superb. I had trouble finding a solid threshold to detect a non-human response, and more trouble getting it to wait for the beep before playing outgoing announcment. I should point out, however, that this was mostly just an experiment of my own accord, so the testing was rather limited.
As for capacity, they can be ordered with either 32 or 64 port capability, and I don't believe they use any PCM timeslots.
Unforutnately, there's not much in the way of white paper or other docs on the ADCs, but you might be able to get some material from an Aspect rep.