I wonder if such things should be evaluated in terms of the knowledge and experience they gained the company. I would say the Surface RT experience has reflected a lot on their experience and strategy developing Windows 8 and Phone. If (say) the experience is reflected in the level of success of Windows Phone 8, then may be overall it is a net success for Microsoft.

I think every company (like Microsoft, Apple, Google did) need to maintain software and hardware divisions, if only to get the feeling what are the software current needs in an evolving hardware profile.