I obviously don't know the TF2 community well enough, but playing with people who weren't high-pitched racists was a welcome change of pace for a multiplayer FPS.
I've encountered some, but they are very few and far between and are usually the same people who are on Halo. But they are usually thoroughly shunned by the rest of the team when they show their true colours.
I'm talking Medics abandoning Heavies here.
And yes, they have been very supportive. I remember my first time playing engineer and not knowing what the heck to do. I asked for help and the other nearby engineer told me exactly told me what to build first, where to set my sentry, and where the teleporters would be of the most use, along with some other great general tips. I'm still not a very good engineer, but I'm a lot better than I would be if I started off blind.
And yes, all 5 games are thoroughly enjoyable in Da Box. Although, I can't say from experience, as I have yet to play Episode 1 or 2. Stupid Ravenholm scaring the crap out of me....