situation, mabye not directly comparing the 30D to the D100, becuase i think you are going to find the comparison is very one sided....more towards the 30D
take alook at Phils review of the D100, and compare the high ISO and IQ shots to the 30D, you WILL see a very large difference.
the D100 is new a few generations behind, mabye not for Nikon, but Canon has produced a few cameras inbetween there. i think you would be better of comparing the 30D to the XT for your purposes. you can do a quick search on the forum and it should return you many many results on that topic!
the 30D has a larger buffer and better AI servo focusing (contious focusing for sports), and a higher frame rate than the XT, its just the XT is a heck of a lot cheaper.
i would compare them and see hwat you get, but i think yo would find the 30D is miles ahead of the D100 IMHO.
Canons are alos known for the silky smooth high ISO images, where as you are not going to find the same DR or IQ in the D100 OR D200 for that matter as you will in either of the XT or the 30D.
SO, if you are doing sports in semi low light, the higher ISOs will come in handy.
those are jut a few things to consider, i didn't go into detail, so a search and you will find onts of stuff on both.
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-Machu
Yes, I realize speling is a chalunge for sum of us...I am inkluded in that grup, so pleze foregiv me.
The Beauty of IR