I'm running the dual Moroso setup... one can for the heads, one can for the crankcase.
The head can hasn't caught more than a drop, but I haven't taken my car to the track yet, either.
The crankcase can I've had to empty several times in just a few thousand miles.
Worth it? Depends on how you drive, how much oil vapor makes out of the crankcase breather (YMMV), and how much/little you care about your engine ingesting that stuff. The inside of the TMIC on my 09 STi after 60,000mi was nasty as hell... but I also drove the hell out of that car. Commuting, trackdays, hauling motorcycles, ice racing, etc.
There's a 100+ page thread on IWSTI about AOSs/catch cans if you REALLY want to hear the pros and cons...
