I'm in the same boat here. After reading so much about these two, still have not made up my mind. Since I'm not as 发烧 as you guys, I'm not ready to invest as much. Here are the two opposite ideas fighting with each other and drive me crazy:
1. Buy 300D and with the money saved, buy a decent lens. I'm not even talking about L, just a 28-135 IS will be good enough.
2. Buy a 10D and use the existing crappy lens, Save money to get a good lens in future. The reason: 10D will propably last longer than 300D due to better build quality. We propably won't upgrade camera body for at least a few years since the full frame sensor price won't drop so quickly.