Aero Glass Review
It's easy for me to forget that most people haven't seen Vista yet. I've been running beta builds since May and I've been quite happy. Vista isn't as big of a change as 3.1 to Win95 was, but it's bigger than the Win98 to WinXP jump. It will take you a few days to catch up.
The biggest thing that everyone will notice is the shiny new presentation layer called Aero Glass. A picture says 1000 words and since my fingers are tired, I'll choose to give you the pictures.
When you make the jump to Vista, I'd like to add something to your experience. Try moving your task bar to the right side of your screen. Don't auto hide it and make it wide enough to fit about 5 or 6 small quick launch icons on a single row. I have been doing this for a couple years and I love it. I frequently have ~10 windows open at once and that really clutters up the task bar when it's on the bottom of the screen. If your task bar is on the right they just stack neatly and everything is easy to find. Another benefit is that the date/time display will switch to show you the day and date as well as the time. It's a more efficient use of space. Most monitors are wider than they are tall. When you scroll, you scroll vertically. Vertical space is precious. Since you're learning a new UI, make this change at the same time and use your destkop space more efficiently.