I am finding the US Defense Language Institute Persian Course the most useful for my needs. I tried the Rosetta Stone software and the http://www.easypersian.com site before finding that this suited my requirements much more.
The problem I had with the Easy Persian site was that it took too much of a grammar-oriented approach to learning, e.g., first learning everything about the past tense, then moving to the future and finally to the present. I found this unnatural. The DLI course takes a conversational approach so one learn the differences among the tenses as one goes along.
As an Urdu speaker, I start with the advantage of knowing the script and for that reason found Rosetta Stone tiring. Its pedagogical strategy is designed for people who do not know how to read the text.
The experience of other learners may differ from mine. Do communicate your reactions as you experiment with alternatives.