If you don't care about spending an extra £10 a year on electric or having to open a window after 4 hours of gaming instead of 5, then they do have numerous benefits (also they are no noisier than a reference Nvidia card).Not meant to sound like a flame post... but why are people buying these when the Nvidia offering is a lot better on performance, noise and power for a similar price?
At RRP you get a card that can trade performance in games with a comparably priced Nvidia card, while performing in applications like an Nvidia card costing double, and in addition you get support for the VHS of adaptive sync instead of the BetaMax it means your monitor upgrade options are much more varied. Unless you're specifically looking for an excuse to hate on them then they are great cards if you're looking for an upgrade.