I've just bought the Proporta case for N810. Just superb. Looks and feels good and the plastic cover over the keyboard means you can use the IT without removing it from the case. It has a little plastic tab to stop the IT slipping out of the case but I've removed it since the snug fit keeps the tablet in place anyway.
Expensive but with the alu protection and quality feel, worth it, I'd say. No, I don't work for them!