I disagree re: steel frames. All of my bikes are steel, from my race bike (yes, actually raced... well, in the past) to my city bike. The race bike weighs in right around where the aluminum bike it replaced came in.

Steel rides great. Cheap steel will weigh more than cheap aluminum, but is not that much heavier once you factor in yourself and what you carry.

The nice thing about steel is that it's repairable, rides nicely, and fails gracefully (should it fail at all).