Well, as someone who owns a TT bike, I'd say if you want to do well in TT's or Tri's you definitely want aerobars.

If you're not going to be doing either, you don't.

If you're just doing the occassional tri, get a pair of "slam" style aerobars (which are designed to work with a road bike fit) and put them on a few weeks before your tri, and practice with them. Otherwise take them off the bike. (which you will have to do anyway for mass start races).

And it sounds like the OP is going to have to change his bike setup a fair amount to take much advantage of them.