Here is a fascinating discussion for somebody like me who is an avid language-learner:
Pimsleur review by experienced language learner | Fluent in 3 months
Irish polyglot Benny Lewis is even more devoted to learning new tongues than I. And that's saying something. Check out his 8-language pitch for his learning guide.
Currently I'm learning Turkish. I've been invited to give a talk next month to students at Koç Üniversitesi in Istanbul about A Gift for the Sultan, which will by then be published in Turkish, and I want to be able at least to converse a little in that language while we're there. I've been using (mostly) Rosetta Stone, which is marvelous for my way of learning: simultaneously aural and written, but intuitive, no rules spelled out. I cheat, and look in books when intuition fails. Each of us has his/her own learning techniques, but for me it's been working. After reading Benny Lewis's review and listening to the Pimsleur sales pitch (it's online), I'm sticking with Rosetta.