Someone once said that the most expensive bike is the one that just sits in the garage. As long as you're happy with it and it does what you want, whats wrong with that? I have a 2003 Diamondback (the commuter) that I bought for $200. Still rolling!

On the other hand, my road bike is an 18year old Cannondale - you couldn't get me to give that up for any wallyworld road bike!