It supports VST plugins (including an AutoTune plugin) and works just fine on Windows 7 x64. Superseded by the commercial Studio One there is still plenty of activity in the forums to get you started. For even more plugins and information on various audio related topics, check out KVRAudio.
I'm not one for rap or hip-hop, but this free remixed album Gold N' Fly by Alex Kresovich caught my attention. It combines the GoldenEye soundtrack with various urban music, the result is surprising.
You'll also find other videogame/rap remixes there including Final Fantasy and Zelda.