Flashcard-like tools like Memrise, Skritter, TrainChinese, etc. What do you think is the best?

Before you say it:

• I already have a one-on-one teacher
• I already put in a good number of hours of review per week
• I know that full-immersion is best, but I live in the US and won't be leaving my job any time soon
• I already try to speak a little with native speakers, but my speaking is limited at this ponit

I say the above because it seems that whenever a question like this is asked, some take it as an opportunity to say "tsk, tsk" that anyone would ask about tools beyond just using a textbook, a teacher and engaging with native speakers.

So what have you found to be helpful among the above review tools? I find the sheer number of tools available pretty mind-boggling, so any comments you have about your own experience will be extremely helpful.