In Reply To:
Aero trumps weight every time.
I don't agree with this entirely. For the majority of riders on the majority of courses, this is true.
However, there are exceptions. If you are a very weak rider riding a very hilly course, a TT may not be the best option. The aerodynamic effect of a TT bike and deep dish wheels is much higher at faster speeds. If you are a weak, slow rider and spend a considerable amount of time on the course under 10mph, in my opinion (not numbers from a wind tunnel) it may not be worth it to sacrifice the weight.
More importantly, it may not be worth sacrificing your comfort. If you have back problems or very little flexibility, even if it saves you 5-10 min riding in the most aerodynamic position on an aerodynamic bike, you may lose so much more time being completely messed up during your run.
Finally, there is a money issue. You can achieve a very "fast" position on a road bike with clip-on aerobars or bar-end shifters with an aero basebar + fast wheels.
A TT frame with an aerodynamic position will be considerably faster at high speeds, but only if the position is used! In the races I watch/participate in, I see that most athletes do not use their aero position during critical times of the race. Secondly, many riders crank out the uphill and coast (sitting up) on the downhills-a complete waste of aerodynamics right there. Lastly, so many riders are very uncomfortable riding a TT bike in the aero position- they brake and go slowly around corners, sit-up, swerve- another waste of aerodynamics. And potentially hazardous.
I'm not assuming that you are any of these things- what I am saying is that 1.) position is more important than bike 2.) fast wheels are more important than a fast bike and 3.) If you get the bike, ride it to its full potential by getting comfortable with it and working on your flexibility and strength if needed.