Actually it is entirely true because im a developer and im using the SL Beta on my MBA to write this now. Snow Leopard was designed to be a revision of Leopard, not a rewrite, and it essentialy is a slimmed down Leopard with all the same features, but less code, so it runs faster, and more utilisation of the Dual Cores for every day OS tasks.
The Open CL and Hybrid SLI functionality dont really apply to the MBA because it doesnt have a dedicated graphics card, only an integrated chip, however when performing advanced Photoshop tasks ive noticed they are notable faster (double) and the same in Final Cut Pro, so the CPU is obviously offloading tasks to the Graphics Chip, but only graphical tasks, which makes sense anyway. This also helps with gaming.
Overall the computer performs with SL as my 2.4Macbook does with Leopard.