To the point... buy an iPad. We've demo'd both the Slate and the iPad, there is simply no competition. Windows 7 just doesn't work well on this kind of device.
The iPad profiler was an excellent tool, allowing you to build a student profile for your iPad and essentially 'image' it whenever you want and works on Windows PC's. With good educational apps, excellent and responsive interface, it's the kind of device which students would want to use. Check out a company called Stormfront who can arrange a demo iPad for your school. Personally, I've always been a Windows chap and I approached the iPad as a complete cynic so it really is worth trying if you're looking at these kind of devices.
To be a little more positive, the Slate does make a good tea tray.