It looks like ArcSDE 10.0 databases are not yet supported... At least documentation on the geoserver-2.0.2-arcsde-plugin doesn't appear to address it specifically, and I can't get it to work. Is that right?
That's because the 2.0.2 docs predate 10.0. Please be clearer about what you have tried and why it is not working. This email on the users list (http://firstname.lastname@example.org/msg03004.html) suggests it is supported.