I have been super busy studying to get my CCNA and then am proceeding right on to my CCNP, so I have not played in a bit. Hopefully I can come up for air and be around more regularly soon!
I tend to keep it around 7.5, but I also adjust the sensitivity on the fly on the mouse itself depending on what class I am playing.
Sometimes I want a very twitchy responsive speed. Other times I want a bit more steadiness.