After a long struggle, I finally totally got rid them here. I don't think it was what I used, but how I used it. I tried a lot of things, but the mites always seemed to come back eventually. This last time I just used neem... but I was VERY thorough (tops/bottoms of leaves, stems, and even the soil around the plant). I did it every three days, repeating five times. It's been a month or more - NO sign of them. I think in the past I did things that killed mites, but not eggs - and by being a bit loose with my schedule (going 4,5, or 6 days sometimes between treatments) I allowed new mites to hatch, then lay new eggs.
So, my advice is to be VERY thorough and VERY consistent - every three days; no excuses, no exceptions.
I think another factor for me was that I did this particular session of treatments at the start of a new run. The plants were small, and it was easy to really spray every part of the plants.