The Audix D6 has a very sculpted frequency response. It's got a huge low-mid cut and big boosts in the top and bottom. The sound is very clicky and has a lot of sub-lows, but not really any meat. The D112 is a lot less sculpted, and captures a more full sound that can much more easily be EQ'd in the mixdown. As a recording engineer I much prefer the D112 for that reason. The Beta52A is somewhere inbetween the D6 an D112. I like it in the studio, but it's a really great live kick mic. Another mic to check out is the ElectroVoice RE320.
Anyone use the Sennheiser e602? The original one, not the e602-II.