Has anyone had experience with add-on heat managers for hydronic boiler operation? I am particularly interested in reports on the Beckett Heat Manager Model 7512. Do they provide the level of efficiency that they suggest and do they work well in a system that has multizones and a combination of radiant floor heat and traditional baseboard? I have found the 7512 for as low as $158.00 so it seems like a good risk. Any reports?