I've read that now that there's a cure for hep-C, NASH from NAFL-D is on track to be the most prevalent reason for a liver transplant. Also, fatty liver prevalence (alcohol involved or not) has made having enough livers to transplant problematic as fatty livers do not do well when transplanted. I've seen nothing about how well living donors with fatty livers do post single lobe removal - but that's probably because having a fatty liver means you're not allowed to make a donation.
The liver's an amazing organ. If you take some out, it will regrow. If you transplant that part taken out into someone else, that part will regrow - not into a complete two-lobe liver, but something large enough to handle the entire metabolic load for a person.