I just ran the first playtest session for a post-apocalyptic booklet for Gavin Norman's B/X Essentials I'm working on. All in all, the system seemed to hold up, with a few minor cracks, but I did have some problems with timing.
Due to my players not necessarily being familiar with the system, which I'm not very concerned with, they did take a while trying to optimize their vehicle, and obsessing over rationing gas, which I am concerned with. I'm definitely considering using a usage die type thing like from The Black Hack to try to simplify keeping track of fuel, at least as an optional rule. I'm not sure keeping track of every last drop of gas is great for the aesthetic or the cinematic feel I'm hoping for.
Currently, the party consists of a marksman, a monkey (read: mechanic), an inventor, and a cardinal. The cardinal's player is still trying to figure out how they want to play an evangelical type, but really seems to like the vibe of the class. But the rest of the party is still trying to figure out how they want to use their class abilities and what their class selection means for the character.
We ended just as the party was heading towards the first combat, so that should be fun.