In my opinion, it isn't that great a revision technique, not compared to most other Internet sources and books out there. I would recommend any revision guide or books over it, however it can be useful for sciences (If you don't have the revision guide, that is.)
i think it's good if you want to do a quick bit of revision and recap. i only use it for the sciences really and i found it useful.
but be careful how much you use samlearning tho, use it in combination with other techniques i'd say because im dubious about how much actually sinks in