I just purchased a BK Warrior 9920 in September and it let the smoke out on it's first use after 10 minutes.
I was running it in an e-Revo on 4s geared very conservatively. I was even driving very conservatively. I had the black jumper removed and was using a UBEC. Batts, Motors, and controller were barely warm at all.
In other words, they're a great deal at only $125, but not if they only last 10 minutes. Now I get to enjoy the famous BK service experience.
On the other hand, years ago I had a 9918 that ran like a champ. So YMMV. I'll probably just keep the MM for my e-Revo and buy the new Sidewinder for my Rustler. The MM/9XL combo works perfectly on my e-Revo on 4s lipo.
(For the record, this fiasco is in no way RCM's problem. It clearly states in the product description that the controller is being sold so cheap because it doesn't come with any service warranty through RCM. I just want it to be clear that none of this affects my relationship or love for RCM.)