I know a small part of the 145 world.
Joined the USN back in '76 and got out in '80. Worked as a Weapons system Tech on P-3Cs. After that I did a number of different things and got a BS degree which turned out to be a waste of time. I subsequently went back into electronics, but was very dissatisfied with most work environments. I wanted desperately back into the world of aviation.
My break came in 2004 when I hired on with my present employer (a Part 145 Repair Station). Things rapidly changed the first two years, and I became the first point of service for a manufacturer of fiber-optic gyro systems (AHRS). These systems are found in Cessna 560XLs, 750s, 680s, Learjet 31As, 45s, CRJ900s, the military's current T-6, the CL415, Pilatus PC-12s, some of the M28s, and a few other fixed wing aircraft. They're also used in Bell 412s, Sikorsky S-76s and -92s, AW-109s and -139s, and a number of other copters. The beauty of the setup is that outside of continental Europe, all these systems come to yours truly. Many operators send them to big outfits like Honeywell, but ultimately they come to me, personally. I work every one of em. What cannot be repaired in my shop is returned to the factory in Europe. It can be a very interesting gig.
As far as Part 145 goes, I've become quite familiar with many aspects of it as an in-process inspector (we do many things other than AHRS systems) and a Repairman Certificate holder. Many guys can't handle all the crossing of "T"s and dotting of "I"s, but the way I approach it is that by doing everything by the book, I am doing two things: 1. covering my own ass and 2. keeping aircrew and passengers safe. I find it comforting to know just exactly where I stand and what my responsibilities are, and knowing that if I think something's not right or I am not confident that the equipment will perform as designed I don't have to sign off on it. I take that stuff pretty seriously.
Aviation maintenance is a great field for the right kind of person, but it sure ain't for everyone.