Product review (5 stars): I think they help and don't see that they harm
I've taken to putting these on my AC condensers because it seems to reduce the spike of high current at start that makes my lights in the house dim when she kicks on.  I had a contactor relay get stuck together on a 2 year old unit at one of my rentals so I ordered this thinking it may prevent that from happening again so soon.  I gave an old one (removed from service) to a friend who was told that his compressor was shot and was quoted $7k to replace the whole unit in a Chicago loft apartment.  This thing got it going again and its been running for a year so far.