I have a primary bike and a backup bike. The primary bike is a European commuter with a hub dynamo, and built in lights. The backup bike is a Specialized Crossroads with a cheap Cateye headlight, fenders, and a rear blinkie. The primary bike goes about 2,500 miles per year; the backup does maybe 50. However, I'm glad I have it -- it means I can leave the primary at the LBS for a few days for tuneups, tire changes, and the like.

The only thing that gets changed over is the U-lock. Remembering to switch it over is a hassle. I think I should get a second lock for it. That way, I would have two bikes, each ready to go at a moment's notice.

Paul