Not adequately flexible. I can only have 2 heating periods (normal or comfort) in any daily cycle, the third and subsequent heating periods do not function. From Viessman's response, this is by design, and neither the salesman, installer nor Veissman engineer were aware of this. They seem to be a responsible and responsive company, but this really is a huge fail; can the system be changed or updated? Inquire about what you're getting before laying down your money. Mis-sold, unsatisfactory.
ViCare at Google Play market analyse