Scoble explains why you should use full text feeds:

The other thing I realized is that life is too short. If people won't give you their content in the way you want to subscribe to it well then I'm gonna unsubscribe and go somewhere else. It's not like there aren't too many feeds to choose from anyway.

Why is it important? Well, you ever try reading a partial feed in an airplane? It's frustrating!

Even with a live connection, a partial feed requires further action to follow. It's just too easy to say "ahh, stuff it" and move along. Want people to read your stuff? Give them full content. Want them to come to your website? Write something that gives them a reason to. Look at Scoble, for instance. Many of his posts have driven me to Channel 9, and I don't even subscribe to it.