10D to 20D to 30D is not much of an upgrade (IMHO) which is why i held off upgrading. But 10D to 40D is a huge upgrade and well worth the extra $300 for me. It's tough for me to say whether it's a good upgrade for you or not, not knowing what you like to photograph etc. But features and functionality wise, the 40 is far superior to the 10. That being said, if I hadn't dropped my 10 accidentally in January which broke the onboard flash, I probably would have had a hard time justifying the 40. The other big driving force for me was that I am very tired of HAVING to photoshop every picture that comes out of the 10. So far with the test shots i've taken with the 40, I can set the in camera settings (sharpness, color) so that the pics are great right out of the camera, which I could never seem to get exactly right with the 10D.

1 other thing is that I was constantly changing lenses because I didn't have 2 bodies. Now I can leave my 70-200 2.8 IS on the 10D and a 17-40L on the 40D and carry both and avoid lense changes. I'm not big on cleaning the sensor and constantly changing lenses at the beach or hiking etc etc gets the sensors pretty dirty, so having 2 bodies negates having to change.

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