As per the description, suspend does not work (system tries to suspend, then immediately comes back to life). The workaround I found was to toggle XHC off via a:

echo XHC > /proc/acpi/wakeup

This toggled XHC to a disabled state and seems to solve the issue. My guess is that this may be related to the trackpad as I don't think I had this issue until I re-enabled the trackpad (I'm a trackpoint man)

I am wondering if it's a good idea for us to have something like xdm disable some wakeups by default as they seem to interfere with proper power management, maybe via an initscript with a conf.d file where some can be re-enabled if desired by the user.