It mostly depends on the individual airport. They hire locally (of course) and that has an impact on the "culture" that simmers at the checkpoints.
Orlando International? Downright good service from TSA. They smile, they're courteous and polite, they're fast, they'll actually banter with you like a human being. Even the non-pre-check line is pretty fast. Austin, TX's little Bergstrom airport? Just as friendly. Arguably friendlier if it's slow. I stayed (willingly) and shot the shit with them for a good half hour after getting cleared because I was early for my flight and nobody else was coming through the checkpoint. Salt Lake City was pretty good too.
Las Vegas? McCarran International (I refuse to call it "Harry Reid International")? Fuck those useless faggots with a six-foot cactus. Vegas brings out the worst in people anyway, but combine that with TSA "culture" and holy shit dude, you get god damn skin-walking demons. They probably cause more terrorist acts than they prevent. I shit you not, they've swabbed my mother's famous chocolate fudge every time I've flown out of there. They ignore me completely when they do it, offer no explanation, then wordlessly and unceremoniously plop it at the end of the table when they're done. They've never once searched for (or swabbed) any electronics I've brought through. Useless cunts.