My mate says -
"Personally I enjoy DHC far far more than codeine, though that may just be because its much harder for me to get than codeine..
I believe its somewhere around 1.5 to 2 times as potent as codeine, in my experience i would say it feels at least twice as strong, but each of us metabolize things differently.
Also has quite a low oral bioavailability (20%-ish)i think compared to rectal which is much higher, though i cant seem to find out by how much exactly.
DHC lasts much longer which is great, around 6-8 hours,
To be safe you'd want to take less than half your max codeine dose, so you know what you're playing with, and a good thing about DHC is that unlike codeine, more DHC can be taken throughout the experience to boost the high,so you won't be wasting any if you're already high enough, where as codeine inhibits the cyp26 enzyme in your liver responsible for metabolizing codeine into morphine, so once you've dosed with codeine consuming more after the come up is a waste."
Apart from that he says he doesn't know much more, but says have a comfy comfy time.