I'm not so sure about this. Buying a mid-high level card is usually a good idea, but absolute top of the line is a mistake. That Geforce 8800 Ultra cost $500+ two years ago, but is now worse than a $150 GTX 260. Generally better to buy two steps back and pay half as much, and then buy a new one two years later. Not only are you ending up with a better card for the same money, you renew your warranty and might even be able to sell the old one. At the very worst you can throw the old one in another machine and use it as a backup system.
That depends really. Lets take the GTX 260. There are multiple versions of that card on the market right now. One of them is $150, there's another GTX 260 that's still $300. The difference is normally more memory on the card, more pipe lines, faster calculations, faster floating point operations...
When most people buy graphics cards today the only thing they are concerned with is the cost of the card. They don't usually look deeper into the cards specs. As in most things in life, Quality cost more....period. Sometimes there are deals that go against convention but more often then not things that you pay more for tend to last longer and work better. I go with NVidia cards because of the experiences I've had in the last 12 years building my own computers.
I don't want to get into the NVidia versus ATI Fanboy wars. I really don't care to argue symantics or company policy or who's making the best whatever for the best prices. These companies have been the top two competitors since the fall of Voodoo. ATI does make good cards, usually for a cheaper price, but that price always comes at a "cost". Whether it's not as many pipelines, not as much memory on the card, cheaper materials, almost always something. I have bought and used ATI cards before as well. I've owned two ATI cards out of the eight or so cards I've bought in my lifetime. Every ATI card I've ever used has burnt out on me at some point or another, more often then not within the first two years of owning them. Every NVidia card I've ever bought comes with a Lifetime warranty. If it burns out or blows up at Any time because of standard use I can send it back and they'll send me a replacement. It's the same with my motherboard as well. I've only had one NVidia card ever burn up on me. That's one out of six. The other five I still have and they end up going from my system to my wifes, then from hers to my mothers as I upgrade again.
It's the same with Pentium and AMD. I've only had two AMD processors in my life and both of them burned out on me after about 3 years. That's with me replacing the cooling gel every year. I've only had one Pentium ever burn out on me and it took almost 12 years to finally go. What's the difference between AMD and Pentium? Anywhere between $150 to $300.
There are other people out there though who have the Reverse scenario happen to them where every NVidia and Pentium they've owned has been crap, I don't doubt it. If you count them up, then count up the people with experiences like mine, I think you'll find far more in the camp I'm in then on the opposite side of the fence.