These 'very expensive' video cards usually get voted cold because they are 'very expensive'. This deal is aimed at those with a Phenom II x4/x6 or an i5 or i7 CPU, and even then only those who are into high quality, high definition gaming.
This card is the cheapest example available. I recently paid £315 each for two of them.
If you've spent hundreds or even thousands of pounds on a super fast PC but you have a cheapo budget graphics card, your system will run no better than if you'd got a cheapo system. £50 to £100 graphics cards will be the bottleneck of i5 & i7 based systems, that is, your system will only run as fast as the slowest component allows it.
This card is judged by most to lie between the performance of an ATI 5850 and a 5870. But with AA turned up (AA=anti aliasing, smooths the edges of graphics to remove jaggies), this card will usually match or top the 5870s performance. Most retailers have the 5870 priced at £315 - £330, cheapest I've currently found in stock was at £305.
If you are interested in 3D stereo gaming, this is the only show in town and it is awesome. If you're not, check some of the benchmarks and reviews to see how the games you play compare, if you only play crysis and stalker then you'd be better with the 5870, for almost everything else with AA turned on, this matches or trumps the 5870.
These cards run 10% hotter that the ATI equivelant but with proper cooling installed I've never got this card to exceed 85c in an sli system. Reviewers got it to 93c compared to ATI hitting 85c. Bear this in mind, you may want to add the cost of a couple of case fans if you don't have any, but you would want to do that with the 5870 too.