I actually found the opposite when I visited the US for the first time last year. I was slightly nervous about encountering the TSA as I'd read some absolute horror stories online (many through Hacker News). But I've got to say, the TSA agents I encountered were incredibly friendly and helpful, even chatting and joking with my wife and I^.
Of course they did break into my suit case and destroy my pad lock but hey ho, at least they left me a friendly note.
Anyway I think it's important that both sides of the coin are represented here, people are more likely to write about negative experiences in general.
^We were on honeymoon in Orlando which probably accounts for the generally positive reception :)