Last night I bought the Fuji discs from Best Buy and the TDK ones from Target - after taxes, the former costed me $1.23/disk (since I had a $20 gift card from Best Buy), while the latter costed me $1.59/disk. I have also ordered the Memorex combo-pack from Circuit City, which should be here soon.
Only the TDK discs are certified to be 4x - the Fuji ones don't have any speed ratings printed either on the package or on the discs themselves, although the Best Buy web-site lists them as being 2.4x. I'll try burning a few of these in the next few days, and will post the results after that.