My bike's aluminum. It's what I could afford.

It depends on your susceptibility to road buzz and the roads you ride on. My aluminum road bike doesn't give me a problem on the roads and bike trails back home. It's a bit more of a problem on the roads here (which are ill-maintained), and when I rode the equivalent (unisex model, I think, and a few years older) on chip-seal roads... I now know why they invented carbon fiber.

There's nothing wrong, per se, with aluminum. Like many other things, frame material is a personal choice. You need to balance performance, comfort, and cost.

Bike Chick: Beautiful bike!

Alisha: I know other people have answered your questions, but I sort of want to throw in my two cents:
1) No, you're not crazy. One of my friends went on a sixty-mile ride with NO cycling experience. (Longest ride before that: Four miles.) Now, that's crazy.
2) I'm planning on doing a century one day on my $750 (USD) road bike.
3) A bike's a bike. Riding can't hurt you (unless you overdo it, of course!)
4) For that distance, I'd want to be clipped in (if you mean clipless). I don't know that I feel more secure on descents (that's something I'm working on), but what I do know is that ability to pull up takes some of the work off my quads, and I was grateful for that during my last really long ride.