Pros: Really fast, compatible with all OSs, easy to WC, overclockable, really good value if you know where to look
Cons: Gets incredibly hot, a generation back, fan can be noisy
Now that the 4xx series has been relegated to Fermi history, you can get some really good deals on these Asus cards - just search around for one and you can get a cut-price deal on one.
Framerates are incredible - under water (which is a little fiddly but well worth it), it just storms ahead of the competition. However, it's not in the GTX580/590 league, which is a shame. About equal with a 570 though.
The big issue is that of heat. You could fry an egg on this card when it's really working (and indeed someone has). WCing helps, but give it plenty of radiator space - 240mm to itself if you can.
On air, the fan gets really, really noisy, but from the paragraph above that's not unexpected.
Overclocking the card on water is as easy as opening Voltage Tweak. Read around so you know what's sensible, but under water I got it up to EVGA Superclocked levels quite easily.
With Kepler round the corner, this card is a real bargain - and if you're not after the nth degree of speed, it'll power up to 2560x1440 quite happily. At the prices they sell for now, you really can't complain.