I switched to the present tense halfway through my fic writing for the shorter pieces; for my longer Voyager stories (currently working on Part 3 of a trilogy) I still use past, for consistency's sake. I love the immediacy, although recounting past events from the present tense can give you a headache.

I'm about to try my first "first person" piece, for a Voyager secret drabble exchange. Can't see myself doing it more than once, though.