Well, here are some of the reasons I like Rosetta Stone French (homeschool version), which I purchased about two months ago after spending a couple of years looking at other programs:
the children can do it independently (even my 6 yo)
I can sit down and work on it, too, when I feel like it
the program tracks their progress for me (and you can print reports, should you wish to)
they are forced to learn how to pronounce things properly, as the program requires repeated attempts if things are not said correctly
I can choose the emphasis of each child's program (so, for example, I have it set up for my oldest two to be working on all strands of language, but for my little, it's mostly oral)
I don't have to schedule the program, though I can if I want to
It's simple and fun -- there are never complaints about doing French -- just competition for time to do it on the computer
my children's french vocabulary is definitely improving. Just last night, when we were out for a walk, my son started pointing to things and naming them in french. While I know that doesn't mean they're speaking in french, they are learning basic sentence structure and vocab, and my dh (who is fairly fluent in french) says that building vocabulary is the key at this stage -- just as it was when they were first learning to speak English.
they learn how to listen, read, and speak the language all at the same time
they can listen to themselves speak (by playing back what they've said) in comparison to what the voice on the program says
I'm sure I could come up with some other reasons, but duty calls . . .
HTH
:D