Those are certainly really good questions, Michael, and I don't have any solid answers. These are design choices that we need to think about. There's a risk of providing so much choice that it would become unusably complex.
Maybe Malte's thought about this. He should - he raised the issue, after all! (you're stuck, Malte!)
BTW ACES allows you to get alerts for postings by a particular person, I think. More arbitrary criteria - i.e. search strings - could get awfully expensive in terms of server effort. Selecting alerts according to categorization criteria would be less expensive. But this requires good categorization.
As far as what to expect in a first release, I think we need to hammer out a basic design for the package and those plug-ins that fulfill its contract requirements. This is crucial. Plain e-mail alerts and a few basic packages hooked to it is probably all that's likely to get done at first unless OpenMSG, Malte, or others with a serious need are able to devote considerable effort to it.
