Ok - Ive been looking at the cards I have and the cameras I use them in, and im trying to figure out which to use where (i dont like swapping as to avoid numbering issues)
I have a
40D
20D
and a
IR XT

Currently, I have 5 cards that I use regularly
12gb Extreme 3
4gb Extreme 4
4gb Ultra II
and 2X 2gb ultra II

So I figure that the 12gb e3 will be used in the 40D. its the main camera and needs a fast big card..
Now the question is what to use in the 20D. The buffer on it "sucks" so I want to use a fast card, but Im torn between using the 4gb E4 in it, or keeping it for a backup to the 12gb E3 in the 40D and using the 4g Ultra II in the 20D, but I've discovered that the 4gb UII is kinda slow in the 20d
Also, I was thinking of using the 4gb UII in the XT..
Thoughts?
I was also thinking of getting another 4gb e3 as a backup for the 40D, and that would solve pretty much everything

Well i really dont want to get the numbers from my 20D on my 40D. Gives me a little bit of an idea of how many shots ive done.
Its not to hard to format cards before using them, and then I can use anything in any camera, but having specific cards makes it easier to keep track of them too

I know
ive only had a few times when I needed both 4gb cards, but the 40D is faster so i dont know if ill fill it up enough to warrent a "backup" to the 12gb
I could also keep the 4gb E4 for backup and use the 2 ultra II 2gb for the 20D, and the 4gb for the XT, or even use the 4gb E4 for the IR and keep the ultra IIs for the 20D as I dont think ill use it AS much now
(this is why im so confused myself! so many options! Dont know if the E4 would be better in the 20D or the XT, but I dont think i want to keep IT for a backup. waste of a FAST card...)

This is my basic idea
Only problem I see is my fastest card is in my slowest camera :P
The 20D will be a 2nd lens body, so it should see similar usage to the XT.
I figure in option one, the 20D wont be bottle necked by the card, and the XT has a better software capability to write to the card, and they will be about even output wise..
Option 2 is more of a 20D not being used, fast card for faster camera..
http://www.imagingphototech.com/Ccard.htm