Tech-Hounds.com has published the second part of their SLI: Myth and Reality article

Last week, we took a quick look at what NVIDIA's SLI has to offer. In that article, we concluded that while SLI does work, you should not expect tremendous gains in frame rates. In average, SLI can only offer around 30 % increase, occurring mostly when AA and AF are enabled. However, performance is not the only feature of SLI. In addition to multi rendering, SLI can be used in SLI antialiasing mode. In this mode, the two graphics cards will perform antialiasing with slightly different sample patterns and then combine the results. Once you've enabled SLI antialiasing in the driver panel, you have a choice of either SLI 8x or 16x AA. Technically each card is only rendering 4x AA, so with SLI 8x you can get 8x AA quality at close to 4x AA performance levels. Furthermore, since we're not computing two pixel samples (remember the 'S' in 8xS), SLI 8x will probably be faster than 8xS even in SLI multi rendering mode. We'll be looking at this in the later parts of the article.

SLI: Myth and Reality Part 2