I think that with things such as memory cards, you never know what you’ve got till its gone and gone along with all your lovely pics! Me I use extreme III cards and have never had a problem. Price wise, they are middle of the road. I think that apart from reliability the main difference between cards is the speed of data transfer.

I use a max of 4gb cards and spread out a set of pictures between two cards (I’m lucky in that my camera takes two at once) the idea being that if one card fails then I’ll still have pictures from that location on another. I choose 4bg as a maximum again so as not to have too much on one card.

After a shoot, I’ll copy the images to two separate locations and verify that they have copied before clearing the cards.

With the 40D, shooting RAW you’ll get approx 320 images per 4GB card