I've taken the 102 the full route to IAH and back probably 100 times. I can count on one hand the number of times it was late.
I've taken the 50/88 from downtown to Hobby and the 73 from either Greenway or the Fannin Rail station a few dozen times. Same. Those routes run a local transit coach (unlike the 102, which is normally an MCI highway motorcoach).
Neither traverse a sketchy part of town. It's just they are parts of town with low-income non-whites. Many interpret that as quite scary. The only time I was exposed to violent crime in Houston was in a wealthy area of Spring.