Duolingo, Wlingua, and those apps

Duolingo, Wlingua, and those apps
 

What do you think about those apps? Wlingua, Duolingua, etc.

For me they are cool to go over some things... to reinforce some week areas, or to keep the memory working (vocabulary), and maybe to practice some listening and pronunciation.

But I've found that they are not usefull at all to practice writing and to be fluent (writing or speaking).

Have you tried them?

I never saw any of these before. I tried Wlingua, whose entry test seemed really good a evaluating a student's proficiency, but the following lessons seemed much simpler than the level I was assigned.

I think this course can be helpful, but there is no substation for actual human interaction.