Buddhism isn't a religion, it's a philosophy.

Maybe some, or most of it. But Lamic Buddhism (that which follows the Dalai Lama) is most definitely a religion. Look up its similarities to the Catholic church.

They believe in Karma and Darma, though, which I don't believe in (since it insights that we're being watched or something).

I think they look at Dharma more as a natural force than an entity.

most people who are very religious (that i meet at least) are very happy...

I'm just nitpicking, but how do you know? I live in San Antonio, so nearly everyone's Catholic. The highly religious ones here give off very happy vibes, but knowing some of them shows that they're generally the exact opposite. I think the rules of religion are inherently suppressive of human nature, so the ones who are truly happy might be the aberrant ones.

This is an agnostic speaking out his ass, mind you. But does your experience match mine?

The best thing about the Truths and Path is that you don't need to be a Buddhist to believe in them. They are generally good rules for living, without overstepping the boundaries of what a religion should do. Also, Buddhism is one of the only religions whose policy is to defer to science in event of conflict. That's badass :]

EDIT: Also like the Samsaric realms. Very elucidating to contemplate which realm you might be in.