I think one thing to keep in mind, is that Microsoft has an alternative vision of the tablet. Where in many ways, the iPad and Android tablet's are essentially blown-up cell phones, the Windows RT experience is an attempt at further bridging the gap between the 'small' mobile device experience and the larger desktop/laptop. The obvious advantage with Apple's approach, is the application availability as well as the lesser hardware requirements. With the MS approach, the operating system is 'heavier' supporting a huge library of USB device drivers, the MS Office environment, larger display screen, and etc.
Both approaches are certainly valid, and your own personal use case probably determines which device you're going to be happiest with. In my case, I had an Andriod tablet and an iPad, neither were complete answers to my questions so I gave them away. The Surface seems to come much closer to what I need. I've not taken the plunge yet, but so far have not seen anything that turns me away. Windows RT is certainly not a mature product and there is a lot of room for improvement, but I think MS will be there for the long haul and I expect rapid improvement.