ZOTAC really seem to be on top of the graphics card releases. We only started seeing their products last year but they seemed to get the hang of making a good graphics card pretty fast.
As with most companies they have their standard reference design card but they also have their funky overclocked models. Sure there are plenty of other manufacturers with OC models such as ASUS who have the TOP line-up of cards, while Palit have their Sonic line-up.
But what makes ZOTAC stand out so much with their AMP! line-up is that the clocks they tend to put on these cards are very aggressive and really make it stand out from the competition. We saw that the 9600GT from Galaxy performed around the same as a HD 3870 with stock clock speeds; with the increased clocks on the ZOTAC AMP! Edition 9600GT we will have to see if it can consistently take the lead.