I've done 3 cycles. First one was something like 9 days @ 400mg, the others were far shorter (3-4 days). I lost some bf everytime, but it's REALLY REALLY hard on you. You just feel like total shit on it, all the time. You can't sleep, you sweat like you're in a sauna and you can forget about training. Results are good, but I don't think it's worth it. I lost something like 5lb in my 9 day cycle, once I recovered from the DNP.
I wouldn't do it anymore. Ever.