I normally find that it’s a matter of commitment. Learning a new language is never easy, and for the people looking for a quick-fix, they are often disappointed because they’re never going to be able to find one. On the other hand, people who are serious and inclined towards working a little harder often find success no matter what method they chose because they put the time in.
From what I hear, Rosetta is a good program because it uses immersion which is one of the better ways to learn a language if you’re going to be traveling to a place that speaks that language.
BTW, the best advice I ever got about learning a foreign language- have a glass of wine (or a beer). It’ll help loosen you up, which is a big stumbling block for a lot of people. Good luck