I'm currently using Tribe5 and I found exactly this "problem". Since there are "Desktop Effects" enabled by default, there should be at least a notice in "gnome-appearance-properties" -> "Desktop Effects" that they are only available for the first user of the X-Server-session.
A simple "Desktop effects could not be enabled" is IMHO not sufficient enough to let the user understand why there is no eye candy.
I'm currently using Tribe5 and I found exactly this "problem". Since there are "Desktop Effects" enabled by default, there should be at least a notice in "gnome- appearance- properties" -> "Desktop Effects" that they are only available for the first user of the X-Server-session.
A simple "Desktop effects could not be enabled" is IMHO not sufficient enough to let the user understand why there is no eye candy.