The ShadowKeen trilogy is a superb example of how an author's style can mature and utilize feedback to improve quality.
The first ShadowKeen episode was full of glitches, frustratingly huge levels, ambiguous goals, and a few visual nightmares. ShadowKeen episode two was a vast improvement, with a cohesive story, creative use of the environment, sadistic use of door puzzles, and overall fun factor raised a dozen notches.
ShadowKeen3, by comparison, feels more like an official Keen game than any mod I've played. Ever. There are secret areas everywhere, an all-new alphabet to learn, moderately sized levels with plenty of visual variety, and witty signs asking "How did you get here?"
The learning curve has a couple of spikes in it, and (as with any game) there are a few choke points that will discourage the most casual gamer, but for the most part this mod is WELL worth the download. If you have Keen3 and are looking for a mod that makes the game it's based on look like tripe, pick this one up. Strongly recommended!