I am using the Hitachi 4gb Microdrive without problem.
You'll need to make sure you get a netCF with a type II connector on it. Gumstix has switched to a type I only connector for the future. Not sure when the cutoff is though. If you already received the board it is prolly ok. If you need to do production of something in the future, you may need to get a special build.
The Microdrives seem to work just fine in the boards I have. The gumstix may need a 'modprobe ide-disk' if you use an older buildroot. The current buildroot on SVN takes care of this though.
If you have problems, you can mesg me directly.
----- Original Message ----
From: Landon Cox <firstname.lastname@example.org>
To: General mailing list for gumstix users. <email@example.com>
Sent: Friday, October 13, 2006 3:36:22 PM
Subject: [Gumstix-users] 4GB CF Microdrives