I can already get the bulk of that out of a ~650USD Mac Mini running Mac OS X 10.4 "Tiger". No having to wait an extra year.
I also don't have to worry much about viruses, email worms, or the latest security patches for Internet Explorer. I don't care why that is so much, because it doesn't change the fact that it is the current situation. I also like that things tend to Just Work(tm), and I don't really have to mess with them much. It's a nice change when your occupation involves running around trying to deal with various Windows stupidities.
Not to mention the space savings of the Mini, at about 6.5 inches square and 2 inches tall, it barely takes up any space. It's practically silent unless you're using the optical drive to boot. Still, maybe the biggest bonus if you have to get a new computer anyway, is that the max power draw of the Mini is a whopping 85W. That's less than you might use in an overhead light. In these days of ever increasing energy costs, the Mini can pay for itself by way of utility bill reductions.
I'm sure once Vista's out, Microsoft can focus more on getting work done on the various features they chucked overboard to try and get Vista released next year some time... And once that's done, it might bring some interesting things to the table... But best estimates would put that probably at least an additional year past the release of Vista, and more realistically, probably more like two. Most of it will probably find its way into the server version of Vista, and then eventually trickle down to the consumer oriented version. But unless someone's planning on buying a new system, I don't see the point in Vista. Especially if you're already running XP. Then it's like the whole 2000-XP upgrade, in that it's mostly cosmetic.
So, I know I'll be ordering my Mac Mini here soon and probably just leaving my PC running XP.