This site is a bit dated now....but shows a CF comparison database...select your camera model, in your case 30D, from the pulldown on the top right...it then takes you to the card performance tests for that cam.

http://www.robgalbraith.com/bins/multi_page.asp?cid=6007

Agree with folks here...unless you are shooting bursts...don't bother spending the extra bucks for the Sandisk "Ducati"...
You will notice some performance boost in reading the card in your PC  card reader though.

Martin is also correct regarding cam write speed........but many cams aren't even capable of writing as fast as the cards capability.  The newer, high end DSLR's can and will require faster CF cards to keep up in burst mode.

I'm still using the Ultra II's in sizes from 512 to 4GB...In both my D70 and D300.
The 2 and 4GB are available for a song now....I picked up some 2GB Ultra II's for $19 and some 4GB for $39 recently...I suspect they are even less now.  For interest...the first Ultra II 512Mb I bought several years ago cost me $90!
BTW, beware of purchasing these cards on "auction" sites....many fakes around....

In youth, we learn....with age, we understand.