We bought a Dyson, sent it back for a replacement (thinking we got a lemon) and finally sent it back for good - it just couldn't keep up. We have four beagles and three cats, and I vacuum every day. We test drove both Meile and Riccar, and went with the Riccar upright for performance and price. The only drawback is it's heavy, so we bought a second Riccar for the upper floors.
I know people really love their Dysons, but if I were you I'd see if I could borrow one first to make sure it really will suit your needs. Also, check in with vacuum repair folks and get their opinions on any model you're considering.
Good luck!