How about getting double sli to work well?
That is irrelevant. The only way you can find out whether double SLI works well or not is to buy two cards and try it out. At that point, nVidia's interest in you ceases, because you've bought the requisite 2 video cards.
Now you can buy a THIRD videocard, and then find out that doesn't work either! Feel the excitement!
I still love how 10 years ago, we tried sli and decided it wasn't really such a great idea, and now nVidia brings it back solely for the purpose of selling people 2 videocards, and everyone jumps on the fucking bandwagon and hails it as the best thing since hookers.
PS : my little intelligence monkeys from the future reveal that nVidia plans to launch QUAD SLI by 2010!!!