you missed another MAJOR piece

As of this writing, dual GPU graphics cards like the GeForce GTX 295 are not going to work with Lucid’s HYDRA technology in the way you want it to. Essentially, because the two GPUs behind the PCI Express bridge chips on the graphics boards (both NVIDIA and ATI) are “hidden” to the system, the HYDRA driver will only be able access one of them. This is a bit of a letdown for us as the idea of having a single GTX 295 and then throwing in an HD 5870 sounded very appealing, it doesn’t appear Lucid will be able to get that working.
and overall the performance isnt that impressive yet. 80% scaling for identical GPUs, and looks to be using only about 70% of each GPU for other configurations. so if i had a 4850, and add in a 5850, the difference between them might be too much, resulting in a 10-20% gain (the 285 test got 32 and 52 FPS in their benchmarks, adding in a 250 they go up to 38 and 65 FPS.) so it looks like if you have one card, and plan to get another, it might offer better performance to just get an identical one.

i would like to see more tests where its compared with Xfire, since they can mix and match cards better than SLI allows