Well, I'm at that age where the cool factor has given way to the practical factor. I have two bikes: One is an ultra high end mountain bike, the kind that only weighs 23 lbs, and the other is an old cruiser that a neighbor gave me.
The mountain bike sits in a room collecting dust and never gets used. The cruiser is what I grab when I need go somewhere. I call it "the parts bike", because I use it to go get parts for the car when the car is disassembled. 😉
Riding position: The mountain bike flat out hurts my neck. The seat is way up high and the handle bars are way down low like a typical racing mountain bike. Like I said, it hurts my neck to ride it.
The cruiser: It ways a ton, but it's nice and comfortable with it's high rise handle bars giving me an upright riding position and it has the great big seat. I could ride it for 50 miles and never get tired. It's not fast though; it has the big white-wall tires and a coaster brake. If I needed to stop real fast, I'd be dead. 😱
Road bikes: Yes they are fast, but they are so hard to get to fit. If they don't fit you just perfectly, you're going to be in pain. That's why the professional athletes have their bikes custom made to fit them and only them. A road bike can be comfortable if it fits, and flat out painfull if it doesn't. I caution against getting one unless you're going to make a hardcore hobby out of it. 😎
Hybrid/Comfort bikes: These are the perfect compromise between fast and comfort. Faster than a cruiser and not something that's going to put you in a world of hurt after 5 miles like a mountain bike. They have the high rise handle bars and skinny tires. So if you're using a bike for transportation and not trying to win a race, they're the way to go. 🙂