I also have an 11 mile ride. Going to work, I don't kill myself, but I do keep the pace. I reckon that I have to get to work, after all....
And I have the luxury of a shower where I work.

On the ride home, though, I change things up. I'll extend the distance some times, or sprint through certain sections, or climb a few extra hills - you name it. I started commuting to get the exercise. I've since started looking for ways to stretch out and improve my results. 11 miles in and 20 miles home has become a norm.

I also find that my weekend riding is now more for fun. I ride my older Hard Rock MTB-City bike and just tool around as the wind takes me. I stop to talk to people, just kind of explore and usually end up downtown for the early crowd at the muffin house. Yesterday I rode 21 miles this way and greatly enjoyed myself.

So, should you use your commute to train? I say, "What are you waiting for?"