The new Mac-like ability to show thumbnails of documents and running programs is cute, but it doesn't always work--typical of a level of fit and finish that would be unacceptable from a cut-rate tailor. Only in Windowsland will you find howlers like a Safely Remove Hardware button for memory card readers that happen to be hardwired into your computer.
Should you upgrade your current machine? Are you nuts? Upgrading is almost always a royal pain. Many older boxes are too wimpy for Vista, and a "Vista-ready" unit Microsoft upgraded for me could see my wireless network but not connect to it. The diagnostics helpfully reported "Wireless association failed due to an unknown reason" and suggested I consult my "network administrator"--me. Yet I've connected dozens of things to that network, including other Vista machines, a PlayStation 3 and Microsoft's own Xbox 360.
My recommendation: Don't even consider updating an old machine to Vista, period. And unless you absolutely must, don't buy a new one with Vista until the inevitable Service Pack 1 [a.k.a. Festival o' Fixes] arrives to combat horrors as yet unknown.
As Bill Gates winds down his roles at Microsoft, Windows Vista may be the chief software architect's swan song. It's a shame his legacy is something so utterly unimaginative, internally discordant and woefully out of tune.