I've been learning Russian using the RosettaStone product for about 4 days now, and am happy to report reasonable progress.
The product uses a straightforward and intuitive technique to teach a language. Each lesson is broken into about 10 sections, and each section teaches you a small number of new phrases. By default, each section displays four pictures. When the section starts, it says a phrase in Russian and displays its cyrillic spelling. Phrases are initially just one word, and get progressively longer with each section. When you hear a phrase, you click on the picture it's associated with. If you pick the right picture, you see a green tick mark, otherwise you see a red cross. This process repeats until you have correctly associated all four phrases with their associated picture. When the section is complete, you have the option of going to the next section or repeating the current section.
Sections get progressively harder. For example, the first section mostly associates a single word with a single picture. The second section starts stringing words together, such as the russian for "red car" and "black cat". Sometimes new words are introduced before they have been associated with a simple picture; in these cases, you can usually deduce the correct picture based on the other words in the phrase.
For example, let's say you know the russian for "cat" but not the russian for "black". Assume also that each of the pictures shows an animal of a different color. If only one of the four pictures contains a cat and you hear the russian for "black cat", you can pick the correct picture as well as deduce that the first word in the phrase must be russian for "black".
This approach makes it a fun game, because you're always trying to figure out what each phrase means based on the theme of the pictures combined with your existing vocabulary. Many parents naturally teach kids this way, pointing at an object or performing an action and then saying its name.
I spend about an hour every evening learning a new section and half an hour every morning recapping the previous night's section. I find that even though I don't recall the words very well before I go to sleep, I can remember them fairly well the next morning.
So far, I've learnt about 50 words in 4 days, which is a little over 10 words a day. According to this article, a child learns about 1000 words per year, and an adult knows about 20,000 words. The good news is that a vocabulary of just 1000 words covers around 70% of most written or spoken text, which is good enough for many situations. This means that if I sustain my current pace of 10 words a day, I will gain a usable vocabulary in about 3 months, and if my pace slows to 5 words a day, it would still take less than a year.
I will keep this blog updated with my progress. I'm particularly interested to see how RosettaStone teaches complex phrases, tenses, and verb variations.