I commissioned Cholaster in the past and I had no problem then with my doujins. I've been waiting for them to open commisions again and now that they are open I can say I'm quite happy with the results of my recent commision.
Took 5 days to get 2 doujins fully scanned and the quality/resolution is really good. The time frame might have been due to them starting again after a hiatus + this is not during comiket, so your experience may vary but I can say the wait is worthy.