I can answer this as i use it daily.
Delrin AF is simply delrin filled PTFE (Slipperies material in the world, check guiness book of world records)
Because its filled with PTFE it is alot more self lubricating compared to Delrin 100,200,500 etc etc.
Its also a little softer than regular unfilled virgin delrin, and scratches easier.
It mills about the same.
PTFE is great for bearings but very expensive.. PTFE has Memory so it will go back to its origina molded/milled shape if impacted. its also very heat resistent and easily milled as well.
Nylon i HATE to death, on a lathe it will melt and sometimes fuse back to the part your turning, if you want cheap Nylon/selflubricating material for bushings etc etc, use UHMW, it mills very nicely (not as nice as delrin of coz) its self lubricating and also cheaper than Nylon.
Oh by the way i just joined, i want to convert my Micro-Mark 7x14 to cnc, and i have been reading alot, but have no idea where to start and the cheapest route to go. Hopefully someone can do a "REAL" step by step, blow by blow from start to finish on converting a mini Lathe to cnc.
Check out the stuff i make at
www.island-designs.com
But to answer you question. yes its very good material Delrin AF, although i rather work with regular delrin becuase its a little harder.
Best source i have found for Delrin/PTFE/UHMW is
www.lowcostmetals.com or
http://www.use-enco.com