RS is a great foundation
I have bought level 1-5 in Spanish (Spain), I am into level 2 and I really do think it is a good program, it has supplied to me a good base level understanding of the language, basic vocab and grammer. However, I have been supplimenting it for conversational spanish with podcasts from 'coffee break spanish', which you can download for free. This way I find I am learning faster than I would if I just immersed in RS for 2+ hours a day (I am having basic spanish conversations with some Spanish friends now).
That said, my writing is good and I find I can read basic and spell quite well in spanish (supplimenting with BBC Mundo/other newspaper etc...) but do find listening quite difficult (I still can't keep up with native speakers).
So a summary of RS, so far, would be that RS is very good for learning basic vocab, basic grammer and intermeadiate reading. But as is commonly said I think it lacks somewhat in conversational spanish (but how can you talk to a computer!!!!!! Again supplimenting this to podcasts and a person has gone along way for me!).
This all said I am looking forward to levels 3, 4, and 5!