Not the bike I rode to the pool

When I was a kid, I spent my summers at the pool. I got up early every morning to ride my bike to our neighborhood pool for morning swim team practice. I remember throwing my towel over my shoulder and hopping on the bike to ride to the pool. It was a little bit of freedom and little bit of responsibility for a child. To me, a bike was a bike. Ah, simple ignorance.
Maybe it's because I'm beginning to loathe the treadmill, but I've been feeling lately like I'm ready to start working harder on my swimming and begin riding a bike. I know I can swim. I need to get faster and stronger, but I have not really ridden a bike on a regular basis since I rode one to swim practice.
I've just begun to look around at purchasing a bike. Who knew that choosing a bike was like choosing a car? There seem to be so many things to know. All I want is a bike that won't leave me in too much pain and won't cost more than my car. Anyone know anything about this?
I expect that I'll be spending a significant amount of time with this machine and I want one that is going to be right for me. I'd love to hear how others have managed this task. Did you like what you ended up with? Did you come to love your bike or detest it?
Ride on!