You should blog when you have something to say, not just because you want to critique someone.
Criticism is fine (and I think there is room for a good critique of 37signals). Just pretend that you're saying what you're writing directly to the person in question, and adjust your tone as a consequence.
As noted elsewhere, AMTTI is more of a personal rant board. I'll work on making the content a bit more cogent in the future as I'd like it to mature beyond that...