Boomerang looks like it's quite useful; I like that it's SQL table-driven. However, given the fact that the Pro edition is 995 EUR and it's the cheapest edition that can be used with Twitter, I decided to not even install the demo version - and I love Twitter, most of the time.

Hate to say it, but I could see this as a very useful tool for spammers.

Michael, if you were to include Twitter functionality in the standard version, I think you'd see many more downloads and a big increase in the size of your user base.