Recommendation for scanner APIs

I am starting a development project where I will need to acquire scanned images from scanners with continuous feeders. I would like a recommendation on a programming API to manipulate the scanner. The recommendation can be for built-in interfaces (like WIA) or commercial components. Here are some requirements:
- I need the scanning to be (for the most part) user un-attended.
- I need to support Windows XP and Vista. It would be nice if I could support Win 2000.
- I need the programming interface to be usable from .Net (C# or VB.Net).
- I would like to be able to support a wide variety of scanners.
- I want to stay away from ActiveX components that I need to install. I want .Net solutions.

I have worked with WIA in the past (for grabbing single images) and that has worked ok. My biggest complaint is the small number of scanners that are supported. I have also looked into the new WIA 2.0 features and interfaces and I'm confused as to whether WIA 2.0 is supported on Windows XP and if the same code will work on both XP and Vista platforms. If I use WIA 2.0, do I need to install something on the end-users' computers?

Are there TWAIN components that work well for document feeder scanners? Are ISIS components/APIs a good option?