WMV is actually quite a good format. Quite a lot of people have been using it for HD content for some time now.
I agree that the issue of licencing could be sorted out by downloading the codec for say 200 points.
You have to bear in mind here that MS has the whole Media center business to try and protect. With TVR boxes becoming more common and the xbox able to play multiple formats the Media center market would drop before Vista makes it to market.
A high majority of other formats are used predominately for piracy, there's no reason why you shouldn't encode things, or "backup your DVD's" in WMV format.
What we've been given is a bonus, you couldn't do it before and you've lived with it. MS have said they will continually look at the media functionality, so they are not saying other codecs won't be supported, they are just saying this is a start, and in my opinion a good start.