My first TT this year (it was actually first race, too) I had the same question. I have no aero bars, had no illusions of getting top-10, and really didn't know what to expect in general.

I'd go so far as to say that straight road bikes will be the vast minority. I showed up on my Tarmac, no aero bars, and felt in a way that I stood out like a sore thumb. Nearly EVERYONE had aero bars. Not ACTUALLY everyone, but close. Even then, a LARGE percentage had straight-up TT bikes.

I was at a very distinct disadvantage without aero gear.