One thing I haven't seen addressed so far on this thread is Kevin's initial remark about number of comments.
I have a few blogs and have been involved in others, and let me tell you, especially if you aren't a "leader" in your niche, comments take a long, long time to come. Either people will go comment on you on their own blog, or they just won't bother. It isn't a sign of disinterest, it's just a sign of not-rabid interest.
Until a reader comments for the first time, it takes a real urge to get them to comment. Once they've popped their commenting cherry, so to speak, they'll keep coming back -- on my baseball blog (
http://www.BrewCrewBall.com), I have a few people who comment all the time, and tons of regular readers who never have. Strangely enough, my traffic numbers are just barely positively correlated to comment totals.