NVIDIA's new GeForce GTX 580 feels to deliver what I would have expected from the original GTX 480. The card is blazing fast, especially in newer DX11 titles it often beats AMD's dual-GPU flagship Radeon HD 5970. This performance upgrade helps NVIDIA solidify its leading position in single GPU performance. Another major area that NVIDIA has worked on is power consumption which is over 20% advanced compared to the GTX 480, but there is still about 30% to go to lock horns with AMD's latest HD 6800 Series. NVIDIA has also improved the fan noise of their card, making it the quietest card in 3D load when compared to other high-end cards in this performance segment. However, this does not mean that the card is whisper-quiet or anywhere near it, the card is still well audible but it doesn't sound anymore like "warp core breach imminent" when heavily loaded.
The ASUS ENGTX580 card is basically NVIDIA's reference design with a sticker slapped on it and slightly increased clock speeds. ASUS only increased the engine clock by 10 MHz which results in a performance increase of about 1% - something you'd never notice during actual gaming. On the other hand, ASUS does not charge extra for their card, it's coming at an MSRP of $499 like all other GTX 580 cards. A special feature that ASUS offers with their card is voltage control using ASUS SmartDoctor. Other than that there are no other noteworthy differences in the card compared to any other GeForce GTX 580.