If I'm not mistaking, from the November build, they introduced a new sort of postprocessing which causes the old one to be obsolete and cause great lag.
Been taking part in the monthly challenge for November but, though I would post this here too. http://i.imgur.com/4Wj4hsf.png http://i.imgur.com/vmGvwnS.png
Too bad I don't have the time to participate in this month's challenge. Gonna try the November's challenge. By the way, the concepts look really interesting.