Knock on wood, but i've got a 4GB Seagate (Model #ST64022CF) that i've had for a little over six months now. Dropped it twice, once on carpet, once on a hard tile floor, no problems. It was initially slow in my 20D, until i downgraded my firmware to 2.0.2. i still have the firmware if anyone's interested. i've taken a few thousand shots on it, filled it up a couple of times (raw + large JPEG... never again), and haven't had a problem with it. i keep planning on picking up a 2GB CF card when i catch a good sale, but the MD has done so well it's easy to forget to pick up another card. My only wish is that it were a little easier on my battery. On a full charge with no flash and little LCD usage, i can't fill the drive up unless i shoot raw and large JPEG.
Strangely enough, it worked fine in the XT i tried it in. Supposedly the 2.0.3 update in the 20D fixed a possible write error when writing to some CF cards, but it also made writing to those cards ridiculously slow. i almost returned the MD when i first got it -- IIRC it took 40 seconds to write a raw file, and a half hour to format the drive.