I must first say I don't own an Alpha yet, but I'll be buying an A700 soon.
You can see what difference the SSS makes here:
In these examples you can see the advantage of SSS is quite significant. It's especially nice to have for images taken at long focal lengths (see 75-300 review). It also allows longer shutter times for evening portraits. There's an A100 brochure in which you can find a good example of that. The main advantage of the SSS-feature is that it works with all the Alpha-mount lenses, so you don't have to buy a pricy stabilised lens.
As I said, I don't own an Alpha yet, but I'm sure I always have the SSS on. Just to compensate for some shake. Even if you have a steady hand, it may be useful. So I recommend buying the A100, or even better, the A700. Depends on your budget of course. Sony says the A700's SSS is better than the A100.
- Bjorn -