I can tell you what NOT to buy - any of the Eureka bagless ones. I got one in December, used it three times, and it broke. I called the company and they told me to snake it out with a bent coathanger.
I had to do that every single time I used it, and even then it didn't pick up squat.
Now I'm borrowing a friend's Kirby and I love it, but Nannyde is right, that thing is darn heavy. I'd really like a Dyson. Everyone that I know that has those likes them.