Cons: No official HTC OTA updates. Possibility of unstable if choosing an experminetal rom
Pro's: Quicker bug fixes - no reliance on HTC/Google. More customisable, more control, more personalisation. Faster roms, optimised for performance and battery life - more efficient. Large developer support community. A2SD+, install apps and associated delvik cache onto a partitioned SD card - moves more than standard implementation.