I recently had to go back over to GR to post a review from a GR giveaway and while my feed seems to be less active than it used to be, there certainly still are plenty of people posting there.
I also have to confess that I haven't gotten on LM yet--I'm trying to figure out how to transfer my reviews, since I've gutted all my GR ones and BL doesn't have an export yet.
Long story short, I'm really only here, so I can't compare against the other sites, but now I'm really curious.
I know it's a biased sampling to ask this here, but I know a lot of people here are active on all three. Where do you perceive that most of the activity is happening? Where do you spend your time, and why? Do you plan to keep up the multi-site thing?