New bike?

There's really two parts of this question... First, material. No material doesn't make a significant difference. Steel is a very comfortable material (tends to soak up vibrations really well), but it is of course slightly heavier and it doesn't lend itself to aerodynamics. Weight only matters if you have long sustained climbs (6%+ for over a mile). Aerodynamics of the frame is not neglectable, but it doesn't make THAT much of a difference (it's not 10's of minutes... rather it's a seconds to a minute or so over a 40k..).

The second part is fit. That makes a huge difference (much more than frame aerodynamics), for two reasons. First, the rider accounts for the vast majority of the aerodynamic drag, so a well fitting frame that allows you to be placed in an optimal position can save significant amount of time. Second part of that is the efficiency of the position. The longer the distance the more important this becomes, but it does make a quite significant difference even over shorter distances. A well fitting bike is the most important aspect of cycling. It makes it not only more fun to ride, but also allows you to race faster and longer without compromising your run.

There's tons out there on this topic, but IMO it comes down to this - it's not the wand, it's the wizard.

I read in triathlete mag a number of years ago and it had something about how much faster one would get if they bought a new bike. A very generic answer was given, then the author reminded them to work on their engine, because "remember, Chrissie wellington could still beat you on a huffy." That line has stuck with me for years.

There is no doubt that triathlon is a sport where you can in fact buy speed, but it's for relatively marginal gains.

IMO... If you have the money to spend, buy the tri bike. You won't regret it. It will make you faster and you will be more comfortable on the bike and the run. I started racing on a road bike and two races in decided to take the plunge. I have a specialized Roubaix and a Cervelo P2 and I love them both for different reasons. No offense guys, but that line about working on your "motor" to make you faster, well...sure it's true, but that same philosophy can be used on just about everything you buy, especially in the sport of triathlon. It's basic economics, we all learned about it in high school.