How effective it is?

I have been using SuperMemo for about few years, now I developed MemAid (mainly because of lack SuperMemo on Linux) and I use it everyday. It helps me a lot. My first SuperMemo collection was "Advanced English97" - I have learnt then about 10000 items of knowledge (mainly English words I have never known before) in 6 months spending about 30 minutes a day. And I still remember most of them - thanks to optimal repetitions which are now very rare (few words a day to repeat). Whenever I now learn something, I use MemAid and I don't have to worry that I will forget what is in my learning process in MemAid. Nice feeling, really.