http://www.dpreview.com/reviews/canoneos300d/page10.asp
this is the test done on dpreview.
errr.... b18, i think u got the speed wrong, rite? Rob Galbraith put the speed for Lexar WA 1GB 40x CF as 1.227MB/sec. which means, following ur formula (1x=150kbps), 300D has a write speed of ard 8-9x? sorry if i make a mistake. maths is never a strong point for me.... :embrass:
anyway, i use the 40x Lexar card becos (a) its cheaper than SanDisk Ultra II, at least it's cheaper where i bought it, and (b) at least its future proof, in case canon decides to support WA in their future cameras. at least i dun have to upgrade my CF card. so far, my Lexar has performed admirably in terms of write/read speed. as mentioned, the problem of 'slowness' is not due to the card alone, but also becos of the I/O bottleneck in the 300D. the buffer of 300D cannot handle continous shooting beyond 2-3 fps. this is why a 40x performance is the same as 80x. so, if u are into action shooting, u either have to upgrade to the 10D, 1Ds or 1DmkII. or, u have to be patient while waiting for the cam to write the files into the CF.
that said, whether one wants to buy the 40x now, or to spend more to buy 80x (or Ultra II Extreme), depends on ur future needs. do u want to upgrade from 300D to other higher-end (ie faster cam write speed and bigger buffer) soon? if yes, then spend a bit more to get a faster card. if not, then stick to the 40x or Ultra II.
oh yeah, another thing to take note. 300D's USB is 1.1. ie- unless u're using Lexar's JumpShot cable (which is provided with the CF upon purchase) or a USB2.0 CF card reader, the transfer speed from cam to computer/printer will be slow, irregardless of the speed of the card.