I've been futzing around with a mock-up of the Microsoft Windows Vista interface and I'm not sure I'm a big fan. It's smoother and perhaps a bit more Apple-ish, which is a plus, but the see-through glass can get a bit much. It's nice when you have one window open, but if you have six stacked on top of one another it just gets confusing. Of course, since my eyes are going, maybe it's just me.
However, a really nifty piece of Microsoft Vista is the new TrueType font that the OS uses -- something called Segoe UI. It's definitely an improvement compared to Verdana and Tahoma. So on Windows XP I've gone in and changed the font style for things like menus and icons to use Segoe UI rather than Tahoma. The Segoe UI typeface, in concert with Microsoft's ClearType technology (http://www.microsoft.com/typography/ClearTypeInfo.mspx), makes my screen a lot easier to read. So why wait for Vista? Install the Segoe UI font and enjoy one of the benefits of Windows Vista before it ships.