I have the purple Dyson; I believe it was called the "Absolute Animal" model, because it was designed for households with pets. It's awesome. I have had many vacuums over the years; the last one I had was a Hoover Windtunnel, and the Dyson kicks it butt all over the place. The suction is great, plus the Animal model has a strong beater bar to really help loosen and remove pet hair from the carpet.
On certain types of carpet, or if the carpet is already fairly worn out, the visible difference between the Dyson and another vacuum might not be very obvious. It's not a magic wand, but it does a great job getting all the loose soil out of the carpet. Plus it comes with a full 5-year warranty, which made me feel more comfortable with the heftier price tag.
This is just my experience; there may be less expensive vacuums that do a close job to the Dyson, but I'd do some research first.
at 3:32 PM on Jul. 31, 2010