as far as i can see, most projects that have problems running on different machines have some major bugs created by the developer himself or common issues that you simply dont thought of out of lack of experience... wich will happen in every engine / when using stock-material.
bad written scripts, damaged/wrong-setup media (of any kind), totally offdriven levels near memcap (stay below 1650mb)... bad written scripts^^
(no joke, i have experienced it myself: game wont load, levels crash or did not load... was only a wrong written line in setuplevel and a bad but not wrong written mainscript that produces a useless hud-loop that i used in every level, in addition to oversize the ram of some levels, too > all my fault)
especially the most common problems as crashing when loading next level etc. can be handled with an experienced developer and expanded testing before launching it. and as a tip: write a developer chart with everything in it you do, test your finalbuild game completely minimum once a week to avoid not to know what causes problems now and then.
of course fpsc has some major issues, the main thing is the physics (fall through floors, collision etc) and performance, but as with each other engine you have to say "i have to live with that to get it done". dont try to brake the boundaries that the engine gives, you dont paint pictures outside the frame.
doesnt mean that you shouldnt try anything new, but dont blame the engine when it doesnt work as intended while the engine isnt made for it.
also if the advertisement says something different... you have to be a good developer (=someone who solves problems^^) to get a running game out of this. experience helps a lot, there are some proofs out there that work... more or less

(the foxes, ertlov& wolf-games, alpha-project etc.).