Increased hardware costs, decreases of function (some under the direct control of Microsoft and/or hardware vendors) and some serious security issues are detailed here.
It's a long article. I'm sorry about that. I think this should be required reading for anyone considering buying or building a Vista machine. If even half of the "features" reported on here are true, there will be widespread discontent on a scale not yet seen. And it will all be directed, rightly, at Microsoft.
I suspect there is a possibility all this will work more or less transparently to the user. Then again, this is Microsoft; masters at imposing functional limits on us. I guess the possibility these features won't bother us is vanishingly small.