Re filtering: I guess from my perspective, all I'd really want is a binary filter with two "folders": worth-reading and crap. I'd never look at the crap folder, but you could still say you're presenting me all of the tweets.

Re social: Again, I fully understand where you're coming from. It's a hard thing to balance. Surely in the 3 months of no blog posts, though, there must have been something new you added that would have been worth blogging? It doesn't have to be earth-shattering news, maybe just show some signs of life. Maybe spend 20 minutes every Friday afternoon to mention what's new that week? Maybe tweet one or two things every morning about something semi-related to your service.