I too am a fan of AD2. I have most the ADpaks and MIDI packs which I obtained from several purchases of the Custom Collections (the bundle that allows you to select 3 ADpaks, 3 MIDIpaks, 3 Kitpiece Paks of your choice).
What I like most about AD2, compared to other drum VIs, is the huge variety and quality of MIDI loops, the way in which you can easily and extensively modify them, the large variety of kits/timbres, the plugin's CPU-friendliness and stability, and the relatively low-cost to own (I only paid between $55-60 for each of those Custom Collections).
With just a few 3rd-party plugins you can create some really great drum tracks (and I'm not even a drummer).
The only thing I wish for is the ability to increase the size of the GUI. Thanks to Kamikaze (below), I now know that we can resize the GUI!