Eclectic, you're going to have so much fun! I did a tri in 2004 (very slowly) and again in 2005 (still very slowly) and then took a loooooooong time off and now want to get back into it again.

I think the favorite thing for me is the variety. I *LOVE* to swim (but I suck). I *LOVE* to bike. I don't love walking, but I'm sure I'll love jogging when I lose a bit more weight. And I really enjoy that I'm constantly alternating sports.

You can build up your run gradually over time, but it is quite different after doing a bike ride. Like others said, make sure to get in some bricks where you ride and then run -- maybe starting with a mile. The legs really do feel like jelly at first.