I remember getting on my first aluminum bike at Bike South about 25 years ago. I was riding a steel Schwinn mountain bike, and it was an aluminum Giant mountain bike. I couldn't believe how zippy it was, like it just wanted to move on its own. The memory of that ride has stayed with me.
My first road bike was steel, really more of a commuter. Then after doing some group rides and realizing that I like going fast, I got a carbon fiber Tarmac. It was a great bike, no doubt about it. But after our team switched shop sponsors I wanted to get a new bike that the shop carried. There was a factory closeout deal on CAAD10s, and they had great spec, great value. I was a little nervous about switching back to a metal frame, but went for it.
When I took it for the first ride I was amazed that it felt the same to me as that first aluminum mountain bike I rode - zippy, and like it just wanted to GO. It's possible that it was because the groupset was higher-end than what I had before, but I believe it has lots to do with the frame.
Since then I've been a big believer in aluminum bikes for racing (except TTs, when you really get an advantage from aero shaping possible with carbon fiber). They are strong as hell (for the inevitable crashes), are more resistant to material fatigue (after many many sprint efforts, etc), and are pretty much as light as carbon fiber frames.
They are also a great value. I'm a pretty thrifty guy, so that really is what sold me. The money goes towards the groupset and wheels, where you can really shave off some weight.
I'm pretty happy seeing all the racers on CAAD10s these days, and excited that bike manufactures are continuing to rollout aluminum frames with highend spec. You don't have to break the bank to go fast!