I think the difference in resolution is rather significant, isn't it? I thought the 1Ds2 was 16mp, and the 1Ds3 21mp - I'd say that 5 million extra pixels, or 30% more pixels - is more than slight. But, admittedly, it would not make a "real world" difference for many photographers (although for some of us the extra pixels would be extremely useful).
Another advantage for the 3 is that we can expect Canon to service the camera for at least 4 or 5 more years. That is a very important factor for me.
"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".