I've been using it and I can recommend it. It has a very clean and uncluttered look. It always moves at a pace I like. It's very efficient... not a single second is wasted in navigating around. In the first couple of days of using it, I learned ~200 words. It automatically checks for retention knowing what words I had difficulty learning.
It's strength is also its weakness. It took me ~30 minutes to get used to it. It's just very different from a lot of vocab apps, and IMO far more effective. it's pretty cheap so definitely worth a try.
All in all, it's quite convenient to use my iPhone for vocab. I can use it anytime I like, waiting in line, etc... so I can utilize otherwise wasted time and that helps me a lot.
My strategy is to combine Suvobi with reading if you're a freshmen, sophomore, junior or a senior with >3 months to for SAT. If you're have less time then that to go for SAT, just use Suvobi by itself.
I'm only scratching the surface here. For more details, check out:
SuVoBi.com