I use lexar 1gb, sandisk (extream $ II - 512-2GB), kingston (pros -4gig), and never have had a single card fail, even in sub zero. I also watch buy.com (best place to buy harddrives) or dpreview and often check this site (http://dealnews.com/memory/prices/Compact-Flash/19/4GB.html)
for the best deals. I just saw where adorama has 8 gig sandisk III for 84 bucks with a rebate the rebate ended May 31.
You should buy only as much card as you need. I dont have any of the brand new high speed cards, I sticking around 120x or lower, it's all I really need.