From what I see, Message Center has the most robust filtering options available to use for filtering. It would be extremely helpful if there was a box to filter devices by custom properties.
So there would be a drop-down box to select which custom property you want to filter by and then a text box (or yes/no, etc. depending on what options you have for the C.P) where you can specify what custom property details you want. I could then say, select "city" from my custom property list and then type in "Chicago" to my custom property text box to display my filtered devices with the messages I want. Sometimes we do just want to look at one node or one specific device type, but not being able to narrow this down to a specific location renders the search unhelpful the majority of the time.