Not sure how much of that is a problem - how many meetings do I go to that have iPad users busily taking notes? AFAIK they're not integrating directly into the enterprise network, as long as they've got access to mail they're happy. If you could get a decent version of Office on there...
(Not that I completely disagree - AD integration would certainly be a massive additional advantage, I just don't think it's critical).
Agreed this is a real issue, but a professional buying a device personally is unlikely to care about those bits of the puzzle. Compared to the existing tablet market, Windows RT is significantly better in terms of enterprise integration.
It does support multiple user accounts (yes, not synced to AD, but better than Android and iOS) and FS encryption out of the box. MDM is baked into the platform; again, no Group Policy, but it can be managed through System Centre. It supports the concept of a mouse, it has USB, it can (I think) integrate with Sharepoint.
(Not that I completely disagree - AD integration would certainly be a massive additional advantage, I just don't think it's critical).