I chose to not get a tri specific race bike, but went with a road race bike instead this year after doing tris for two years with the road bike I had.
I didn't think I'd be comfortable in the aero position of a tri bike. Just going to a lighter more aerodynamic road bike made a huge difference for me.
Ride what you have for awhile. If you find yourself hooked, then spend the big bucks. :D
Veronica

