Hey David H, Good to hear from you again... The units are reliable...we have been supplying them for over three years and have only had a couple of failures...mostly of the human type. The units do well in harsh weather (e.g. Minnesota) but are not to be "soaked". We recommend that you use a weather proof cover if they will be exposed to wet conditions. The dimmer is put in line between the transformer and the fixtures to be dimmed; not only does it act as a dimmer but also as a switch...you can dim the fixtures and also turn them off if you like. The dimmer is not to be used with electronic transformers, only magnetic types. These units are not designed for the primary (120v) side of your system either. In that case you are dealing with a totally different dimmer. Rainman, the dimmer will have a impact on your lamps if they are continuously dimmed, we recommend that every week or so you run the system at full power to help reestablish the halogen cycle. Beyond that I have not heard of any other "maintenance" issues that are created by using these units. Anyone needing further information please call me @ (800-609-1130).