All this pro gamer = low sens stuff does my head in.
CSS players played at low dpi for neg acceleration reasons. Now you got DI (direct input) no need to bother. Play at whatever you like. I play really high, got used to it that way so will stay that way. Played with many top UK clans, and some play low, some play high. But most common? MX518 or G5s, occasional deathadder. I play with a rat7 now, and it's taken me a good 4-6 weeks to get half used to it. Bare in mind I used a g5 for 3 years before that.
It's preference - as long as you're not stupid high dpi software limiting, or stupidly low with software enchance you'll be fine. I say 1600dpi+ keep distance for 180 < 10cm (I have it to about 4-5cm). Bottom line is, if you can control it at high freq then you will get shots of faster, but it's more detailed (physical) movements with less room for error.
Get the mouse fix to stop windows vista/7 from applying acceleration (even if you've turned it off in control panel)
S