You know whats better than a "honest" merchant selling most likely defective wares, a merchant who has know clue if their wares actually work!
I love the theme overall, merchants like Dibbler can add a lot to a game by posing an age old question; is it really worth a saving a few coins when there’s a chance my sword will explode? Further complicating matters is the fact you might get a weapon that is better than average. I think the quality system could also be used for weapons the party inevitably scavenge from a dungeon. The writing is the highlight here, and really sells Dibbler's character and the theme.
The layout is barebones, which is both a blessing and a curse. On one hand everything is eligible and easy to follow, which is good, on the other hand it feels like something is missing. The section between the stock and quality tables isn't particularly clear on when a weapon's quality should be tested; I can't decide whether its on or under a natural 13 or 131, which would be any roll. There's also a typo in that same sentence (it should be "..and you roll a natural..", instead there's "...and you a natural...").
Overall, despite these issues, I like Dibbler's Emporium of Weapons. The writing is for the most part really good and entertaining, the theme is great, and the mechanics here can generate some fun moments and as an added bonus, can be easily transplanted elsewhere.