I saw the unit in use at EGCC last summer.On a very clear day it was very impressive to be able to identify all those vapour trails heading northwest to various USA and Scottish locations.Also to see the approaches and departures in and out of Manch.I reckon a roof mounted antenna is essential for best performance but at those frequencies it's not a monster.
I rather fancy one but not sure I could justify it.To those that have them and enjoy them,good on you.