I have had my expectations blow away. I thought this was going to be another iPad clone, and whilst it appeared that initially, pushing the keyboard and having the desktop OS available makes it very attractive for me. The only downside is Metro.
One of the major problems I have with the iPad is the "appification" of everything. There are loads of apps for sure, but they mainly all perform small simple tasks and whilst this is good for your average user, somebody who actually is proficient with a more complex yet much more powerful user interface will have a much worse experience (nothing has yet trumped keyboard shortcuts, once you learn them). Having the desktop OS in the background opens up this tablet for a new market potentially. Apple will remain the popular choice, but there's a market that the iPad is not capturing here by choosing usability over power of interaction.
Pricepoint could be major issue here as well, if they go for a lower price point than Apple (I don't think Microsoft have the power of perceived brand quality like Apple does) than they'll be competing big time, especially given that they will market the fuck out of it. I think it's dangerous for them to try to be in the same price range as the iPad though.