...is that there is no secret. Nothing's going to download it into your brain; you just have to study and practice. I think that's why the Rosetta Stone software and the Muzzy kits are so popular -- because people want to believe there's a miracle cure. I'm sure they're fine, but I don't believe they're hundreds of dollars better than anything else. But they've developed a reputation, a glow, and heaven knows, it's easy to be a sucker for something that makes it sound like it's going to be easy.
Which is why I keep picking up new books on learning Hindi rather than sitting down and spending enough time with any one of them. My latest, mainly because I saw it at such a cheap price used that I was compelled, is Michael Shapiro's Primer of Modern Standard Hindi. For someone of my bent, I find it helpful to get grammatical background, and that's where a lot of the basic intro texts (Teach Yourself, etc.) don't get very in-depth.
I'm thinking it'll be more of an "in conjunction with" kind of book, especially with this "Aargh!" factor: why, dear language learning publishers, do you have all these books that contain exercises for which you provide no answers? This is the most irritating thing ever! I can read through the chapters, but I hesitate to even do the exercises, without any feedback to know if I'm making mistakes. This is certainly not Hindi-specific: I got a Latin Grammar a few years ago, in a vain attempt to brush up my college Latin, and again, there are exercises with no key. Again I say, Aargh!
I was just looking at a book on Amazon called The Teaching and Acquisition of South Asian Languages, with essays by different authors on the subject. One of them is dryly subtitled "Designing a Dictionary of Construction for the Advanced Student," but the main title made me laugh out loud. "Learn Hindi-Urdu in Just Thirty Years?"
That is exactly the lesson plan that I'm on!