For comparison purposes, AMD has increased the 'hundreds' number by one. In their product tiers for the new generation (roughly speaking), 69xx = 58xx and 68xx = 57xx This is definitely a change from the last three generations, where the top-of-the-line were 38xx, 48xx and 58xx. Those were ATI though and now it's AMD, so they did make a numbering change when they took over. Another change will be the new dual-GPU card, which will is rumored to also be a 69xx number, where previously, the 59xx was dual-GPU only. It's a bit confusing, but not too bad once you know what to look for. The 5970 is still the fastest GPU on the market, but it's a dual GPU card and is rumored to be replaced with another dual GPU card in the 1st quarter of 2010. The GTX 580 is currently the fastest single-GPU card on the market.

I've used AMD drivers since early catalyst 8.xx and haven't had problems with any of them that I can recall, FWIW.