Very true Larry, I like it! Personally I find there is nothing worse than when a company launches about 20 tweets at the exact same time and completely sabotages my feed. So damn annoying.
Totally agree about the aggressive self-promotion aswell. We’ve not really put a percentage on it in the past but I’d say we’re at about 90–10 there or thereabouts, which as you say is about right. Enough to get your product out there but it’s not going to alienate people.
The best way is to put on genuinely relevant, informative content and you will pull your audience in.