Hi Derek,
at the moment the Runtime for Java SDK doesn't support ImageService (either from a package or ArcGIS Server service). This is not currently planned for the 10.1 Runtime for Java SDK release.
At present, the REST specification, on top of which the Java SDK is built, does not support FGDC metadata. I don't think there are plans to include this in the REST specification.
The 10.1 Beta 1 Runtime for Java SDK is compatible with the 10.1 Beta version of REST.
However, this doesn't mean that the Runtime for Java SDK can always be uptodate with the full capabilities defined in REST (especially at initial releases such as 10.1)
Gayle