Hi.
I had lots of issues with the ArcGIS EXplorer Version before 2500. I am hoping this new one doesn't crash and doesn't just decide to not show my queries randomly among other issues.
I was really hoping however that this new version would allow you to symbolize by category. I am not sure why you would be able to in ArcGIS Online but not in ArcGIS Explorer. I did a work around in the past by creating different queries for different categories in some data, but as I said before the queries would just decide not to work and I would be missing features often.