I think the IDEA of .NET is great. However, I am skeptical of the security and programming of the MS people as THE END ALL tool. They have a poor track record and often cause issues because they want a proprietary system.
Not that other companies are not the same, but it is something I worry about. Also some of the conveniences still have a programming price to pay and I usually prefer to pay the price myself, so if I am prevented from getting too low level in places, I get nervous.
Lastly, I am concerned that C# and VB.NET do not produce the same CLR. Never got a good answer why not, but it will still lead to some people choosing one language over the other because there will be a performance difference.
All told, however, I am excited. I've done a little C# programming and am looking forward to finding a project to do some more.