My commute is 17.3 miles each way. It's along paved, rural roads with minimal traffic. I can usually start pedaling at home and arrive at work an hour later without putting my feet down at all. Here's google earth's profile of my route. It's certainly alot hillier than I thought it was before I started biking....

Here's a typical stretch of roadway...

All in all it's a great commute and I've dropped about 20 lbs from my former non-bikecommuting self.