I was given a Sebo Duo to try by someone, having cancelled my order for a new one from Restormate on the back of all the negative comments I got when I asked about it on this and Tm'ers.
I've had it a week or two now and I think it's great. Yes, it's light, but you can increase the weight simply by applying more pressure to it as it passes over the carpet. It's a step up from a pile brush and one step down from an all out rotary scrub which can often be overkill. It really brushes the pre-spray into the carpet and obtains better soil release and I think it helps produce an even better result. I like it!!!!
Simon