Is there any reason I shouldn't just get a bottom-of-the-line laptop?

You gotta try Vista. I like it on our machine, runs smooth with no problems at all.
In the next few months you’ll be able to download the next batch of patches so if there are any problems they should be worked out pretty soon.
You’ll be especially OK with Vista if you don’t plan on installing old software or doing lots of crazy stuff right out of the box.