Just got one a couple of days ago, was previously using an ensemble.
Pros :
Works with PC as well as Mac
UAD plugins
Low noise floor
8 channels of audio in
Convertors are decent quality
Automatic sample rate conversion on SPDIF is a nice touch.
Cons :
Build quality is pretty flimsy
Compressed treble end to the sound, not much bass (inferior analog side perhaps), it can get wearing to listen to for extended periods.
Expensive.
Poor routing options in the software control panel (no matrix)
Not a lot of gain for the mic pre-amps or headphone amps (don't go for 250 ohm headsets basically)
Thunderbolt is only used for the UAD bridge, for the convertors/interface side it's all FW all the way even if you buy the TB card (your'e better off getting a cheap TB/FW convertor cable than buying their extortionately priced fw card).
UAD plugins are very very very DSP heavy if you opt to use them.
Latency seems to be pretty high even for FW.
Overall I'd say it's an OK interface, I'm not in love (although honest I am trying to be) but it does the job. I've yet to try running ADAT into the ensemble to make use of it's DA, which I intend to try next (I had hoped to just sell the ensemble but at the moment i'm not sure). The main pro is the UAD plugins if you like them, to me they're just so much digital tonesuck but I know a lot of people swear by them as the second coming and the Apollo just happened to fit the profile (outside of that) and budget for what I was after better than anything else out there currently (sorry RME fans, I can't cope with the DA side on those either although they have excellent software and superb latency), I can't hand on heart recommend it but what I need and hear and what you need and hear may be very different things and regardless of the negatives it is still a good interface with a pretty clean and true sound for the money, so I can't say don't get it either, basically as always YMMV.