I'll also shill for Swordflight. I haven't played any other NWN player created modules and I'm not as experienced a crpg player as some users here but Ive played many of the games the codex considers classics and I feel SF is competitive with many of those classics in many ways. I consider it a must play but you have to enjoy combat because there's a lot of it and it's fairly challenging.
I've completed all 5 chapters over the course of several months and I think I spent atleast 100-120+ hrs in game.
Yeah, Swordflight is truly excellent. It's so smartly designed to focus on single character resource management and tactics - i.e. knowing choke points, understanding all the items you have to work with, making sure you have multiple kits to draw from depending on the threat. It also makes you really understand the rules of 3.5 D&D in ways I never have before. I've played hours and hours of games in D&D and I don't think I ever gave a shit about potentially losing AC points due to wearing items that carried the same AC bonuses, or figuring out saves beyond basics and just facerolling through combat, but you have to in Swordflight.
That's a big part about why I enjoyed it so much. You have to understand the system fairly well to succeed, you have to have a decent(not necessarily optimal) build as well.
I have mostly played dnd crpgs, knights of the chalice 1 is one of my favorite games, did a run right after SF. Also did 2 solo runs of Toee right before I played SF, an IWD2 solo run, a dark sun shattered lands solo run and a BG trilogy solo run as well all in the past few years since 2020. I'd say SF took a bit more knowledge than all those games. I'm doing a BG2 SCS insane double damage run now and the level of knowledge needed is comparable to SF even though it's unfair to compare SF to this challenge run for a number of reasons.
A few other things I like about SF is even if you make a very powerful multi class build, the combat is still challenging and there are some cool RP options and some reactivity even though that's not the focus of the series of modules. I enjoyed the story and writing as well even though some players criticized it harshly and unfairly in my opinion.
All in all, an incredible effort all done by 1 man in his spare time.