well yeah, that's exactly it... the only reason i got all technical and talked about keys (and modes are good to know too) is that most songs that play the same 4 chords over and over (especially if they're open chords) don't sound all that different to others. Though if that's all you're up to, play around with your strumming or picking and come up with a different rythem. It'll make the song sound a lil more original. If you like your G chord, or D chord or whatever... try finding other places on the neck of the guitar to play them, slide them around, use octaves... there's heaps of ways to make a simple chord progression sound slightly intersting.

What i meant by Bdim was a B diminished chord. Diminished chords can sound great in the right song, but they're usually a bugger to play.