Android is FREE and the competition cannot beat the iPad in price or performance.
How does MSFT expect to make a profit, selling a Win8 tablet OS - with high performance requirements, when the competition which uses a FREE operating system, cannot beat Apple?
Supposedly, Windows 8 will come in several flavors, with one or more intended for the tablets, and which would be very conservative as far as resource requirements and resource consumption (battery life).
Thus, it wouldn’t be a power hungry version of Windows 8, but would still offer a better and more powerful experience than the tablets of today.
Maybe they'll deliver something that the other two haven't been able to yet, like the ability to join and participate in a Windows security domain and become an active, manageable part of the enterprise.