No penalty for leaving people on the platform. Originally there was going to be, but it was more fun swapping out people in the later stages to boost your score so we ended up keeping it simple.
Keeping passengers past their stops is usually bad since you're missing out on that bonus, but if they boost another passengers mood enough then taking the hit to their own mood matters much less! (Also I'm imagining the scenario where someone keeps missing their stop because they've got Mr. 5x5 blocking their way and can't squeeze past)
Info on hovering ended up being a bit distracting as you were scrolling over passengers, and would sometimes cover up other passengers when you were trying to click on them. The current system is a bit kludgey, but it mostly works, at least well enough for the jam.
No definitive end, just a score attack to see how far you can get for now. Mid-20s seems to be about the limit for optimal play, though if you're extraordinarily lucky getting to 30 is technically possible.