I think it partly depends on the carpet; most vacs work okay on most parts of my house but one carpet somehow holds onto fluff and only a rotating brush'll get it.
That said I have a panasonic vac and that was (for me) frankly pants all round. The hose falls out if it rotates (which it does easily), the cable retraction system can never manage the last meter or so (in spite of all the warnings about how fierce its supposed to be), its bagless and the filters need cleaning almost every other use, it seems to have a very limited duty cycle and so almost always starts to reduce its own power as you use it, the on/off button has started sticking on and the handle for picking the thing up with forms one half of a larger handle - the other half of which instead pulls out the dust collection chamber and sprays dust everywhere...
I got a £50 wickes wet and dry vac last year, its a fairly cheapo thing as you'd imagine (it's 'tools' wouldn't suit domestic use) and i did get the extra foam filter, but its usefully powerful and good for sucking up stuff like wet hops from the boiler, the dregs from brewing vessels, and with the bag fitted even plaster dust and fine rubble.
Cheers
Kev