it can suck major dog dick at times, not gonna lie. do we hate our job sometimes? yeah. like heres my two weeks notice... do i love my job? most of the time. does it suck that some nonner sitting in the ac/heat who fucks up his job gets paid the same as me? oh yeah. would i trade it for anything else in the air force? not really, only three jobs i can think of are FE, load, or 1A3.
Downtime really depends on which MX job and what base you're at. i only have experience with one base, and being here for over 6 years and seeing people come into my shop from fighters/props, we have it easy as a shop and unit here. we actually get ACC downdays, weekends, and holidays... unless a jet is royally fucked or you are weekend duty crew. AND some times we even get lunch.
You dont really have to deal with QA (passes/fails) if you follow your T.O.... Briefings, im sure we get, maybe a little more, of the suicide and rape briefings then office jobs... probably about the same amount as secfo. Additional duties - once you make some rank you can go to MOC/Debrief. NCOs can get qa, vehicle nco, safety rep, RA, ufpm, etc... if you are a piece of crap then usually CTK or debrief (any rank).
but take this with a grain of salt, as ive said, ive been at one base my whole (6 1/2 yr career) other bases are worse and im sure other bases are a lot better