Before I got my commuter, I only had my racing bike, which was fun, but gave me mild neck and shoulder aches after long rides due to the posture it had me in. My commuter puts me in a more upright position which is more comfortable.

I also ride my bike to work. I love it, but I can't do it more than two days in a row because it wears me out, even though my route isn't that long. If the wear-and-tear you experience disappears with rest, I wouldn't worry about it. Also, remember to keep yourself hydrated during your rides--even if you don't break a sweat, you are breathing faster, which contributes to fluid loss.