Funny, Sli seems to be working reasonably for me. I have some micro stutters as I have always said but Sli gives me nearly double the frame rates of a single card in my setup. With GTS 450's some would think that I shouldn't be getting the results that I have so something with my system must be working. Those that aren't getting the results that they think they should with Sli, try altering the Nvidia Inspector profile to get the best you can until official support arrives (if you don't use N/I download and install it and if necessary make your own profile, or have a look at my post on the subject and use that as a start point).
http://forum.1cpublishing.eu/showthread.php?t=26236