SoCal - I don't think there are many PCs with 4GB in them. That's actually quite expensive, even these days.
I don't see the point in upgrading. A PC is a device for running
applications, no more (for people with a life I mean
).
Also drivers: In my business we sell various bits which need windoze drivers, and vista drivers are very slow to come out. It will be years before there are vista drivers for the more obscure items, by which time the said item will be obsolete so nobody will bother. At this point on the curve, upgrading to vista cuts you off from many add-ons and exposes you to the risk of something you buy being
never supported. I sell into the industrial market where customers will hassle you like mad for a driver.