I bought my S7 Tango in July 2009, no problems at all. It's still basically brand new, the original bag that it came with from the factory is still in there, and it's not even 1/4 full (part of the problem is there isn't much carpet to clean, I've almost filled up the bag in my S4 with the stairs, furniture, car, and hard floors).
I'd recommend it. As mentioned it take a little muscle to pull it back. The brush roll is aggressive but not damaging, really does a nice job on carpets. Super long cord and hose, nice tools that won't damage fabric or scratch hard surfaces, *bright* LED headlights, etc. Since the Tango is an upper tier model it has the electronic power adjustment and the automatic adjustment feature too. And, you cannot beat the filtration, or noise level.
I love mine and will keep it as long as I live. It's quite a beefy vacuum. Holding the handle is like holding a BMW steering wheel.