My opinion, only:

I've yet to meet a real or self-proclaimed "big time" triathlete who didn't think you could buy speed.
I've never met one who didn't tell someone to get a newer, lighter, more aero tri-bike.
Bike shops love them. Better aero, Zipps, helmets, aero shoe covers, the whole nine yards, at retail.
The fact is, you can buy a faster bike. Another fact is that it doesn't always make you faster.
You still have to ride it, and be good at doing so.

Another fact is that it only matters if you're competing against people about as fast as you are.
The people that are faster than you are faster despite your bike, and despite their bikes.

There is a heirarchy to getting faster:
Gearing to your optimum range is money more efficiently spent.
An hour more a week in the pool is time more efficiently spent.
Add another hour a week running, and you'll gain there AND on the bike.
Add another hour practicing transitions, and you'll gain quite a bit.
Know your course and how to maintain momentum in the corners, etc.
Knowing how/when to shift without upsetting your pace is crucial.
Learning to balance the effort you put into each leg is crucial.
Adding a faster bike is far down on the list as far as getting out what you put in.

I see very few folks at the end of triathlons coming in with a photo finish.
About halfway through the run, where you finish is pretty much set.

The best triathlete I ever met rode a DT-shifted aluminum road bike with aero bars.
No one could touch him on the bike, and it really didn't matter what we had.
One of the best triathletes I know, right now, rides a DT-shifted Brew steel bike, full-time drops.

I helped a novice train on a steel bike. She won her age group the first two times out.
She traded the steel in for a carbon fiber road bike. She was no faster, and couldn't figure out why.
She bought a Cervelo P2K, and was no faster, and couldn't figure out why.

My explanation is that she thought she had a disadvantage on the steel bike, and pushed herself harder.
I still believe that. She is a lot more comfortable on her tri-bike, but no faster; actually a bit slower.
If that comfort helps her on the run, then good, but she never attacked with the steel, and never burned out.
On the tri-bike, she about does a hole shot the first 3 miles, can't figure out why she's in O2 debt by 20 miles.
Being relaxed at the start of the bike leg and the run leg, to me, is worth 5 minutes on the bike, 2 minutes on the run.

In longer triathlons, the bike legs simply go to the better riders, period. They turn and burn, no matter the bike.
Quite often, it's over for all but the top two or three by the end of the bike leg. It's hard to make up much time on the run.

At that Olympic distance, the #1 error is going out too fast on the bike, because it not only kills the 2nd half of the bike leg for you, it really kills the run. Get your swim out of the way, establish a decent pace on the bike, and start looking to run down other cyclists from about 13 miles on. Same with the run, get the first couple of miles under your belt, get your stride smooth, and then look ahead for someone to track down.