Without a doubt, Gigabyte has created a fascinating piece of hardware with the 3D1. The concept of creating an SLI setup on a single card deserves the highest respect. Why Gigabyte chose to use the GeForce 6600 GT processor instead of the faster 6800 model is unclear. Possibly, the NV45's HSI bridge chip caused some problems, or such a card would have become too complex to produce. After all, the 6800s use a 256 bit memory interface. Such a dual-core circuit board would quickly become very complex and consequently expensive.
Going only by the numbers, we see that the 3D1 definitely has its pros and cons. Bundled with the motherboard, the card will be slightly cheaper than a comparable GeForce 6600 GT SLI setup, while offering better performance. Also, it will be much less expensive than a single 6800 GT or Ultra card.
However, the downside is that the buyer basically loses the second x16 PCIe slot when using this card. This removes the option of upgrading to SLI at a later time, diminishing the overall flexibility. Therefore, whether or not the 3D1 is a good choice compared to a more flexible two-card 6600 GT SLI setup or even a single 6800 GT/Ultra card mostly depends on the buyer's plans for future upgrades. Whether or not SLI pays off at all depends on the resolutions and quality settings the user prefers to play at. Lastly, the choice of games is important as well: In modern games, a GeForce 6600 GT SLI setup can really shine, offering a tangible performance boost. However, in older titles a single GeForce 6800 GT may be the better choice.
Considering the history of failed attempts at bringing dual-core graphics cards to the market, Gigabyte's 3D1 will probably have some difficulties establishing itself in the marketplace - especially since the card does have some technological limitations. Of course Gigabyte is well aware of this and plans to offer the card - bundled with the K8NXP-SLI motherboard - as a limited edition only.
In the end, the 3D1 showcases Gigabyte's technological expertise and its willingness to innovate. Perhaps the card can be compared to the design prototypes with which car makers try to impress their potential customers at automobile shows. Whatever the case may be, we're definitely hoping to see more of this kind of thing.