As a language teacher, let me just share a few thoughts about Rosetta Stone.
1) Rosetta stone will have you memorize by rote phrases and words that let you manipulate them, but severely hinder your abilities to create the language. When I have visited other countries, the people there are flattered when you speak their language, but if you only know a handful of phrases that are particular to a certain context, it becomes very difficult, if not impossible, to create the language on your own and the people you are conversing with get frustrated.
2) Rosetta stone does not adequately give you the appropriate cultural context in which to use such phrases.
3) It is way too much money for what you get. There are some other language programs which are much cheaper and will give you the same thing.
If you wish to learn Greek, I would recommend that if there is a Greek Orthodox Church near you, inquire whether they have a "Greek school." Such things are for the younger generation (like kids) who are so removed from their Greek homeland, but it may be worth it. Just mho