I personally don't really like Rosetta Stone, although I am basing that on the older version. I haven't had a chance to try out the version 3 software and I'm told it is quite different to the older setup.
What I found was it was quite good for building vocabulary but not grammar or conversation. If you had a spare ten or fifteen years, it might well achieve that. It marketed itself on the fact that you 'learned the language the way a child would learn it' in the beginning and that may well have been the case, but you'd need years to get to any level of fluency with the old system. Like I said, though, the newer version might be of more use.
Having tried I think pretty much every language course system out there over the years, I have to say I've found Pimsleur to be the best. If you're looking for something that will enable you to have basic conversational skills within a few days, that's your thing. I've used several now, am currently going through the German and Italian ones in prep for a couple of holidays this month, and I've found I've done a couple of lessons and been able to go to the country and speak to people. I think they even used to use my testimonial about the Egyptian Arabic course on their site