I'm VERY please with the IBM MicroDrives. I have 2 of the older 384s, which I got with my D1 two years ago, and have run thousands of images through them without issue. I will probably pick up a 1gb now, to supplement them, as I now have a D1x.
As to compact flash, yes, that too could be in my future, but with 3 MDs, I would probably only replace them with the flash cards as they fail (fail? eeks!)