Kenwood decks are good, not great but good. Most common problem I have seen as well as friends is buttons that stop functioning. Their Excelon line of HU's is pretty nice, and definately worth it if you are getting Excelon Amps as well (they integarte with the amps giving more control through the HU). But keep in mind, they are basically like every other company, their lower level stuff will do the job, but the company is really trying to sell the higher end units. If you are not getting Excelon amps, and were considering an Excelon HU, you might want to consider other companies as well in the similar range. Personally, I've found in the lower price ranges Blaupunct, Eclipse, and Clarion have been better, Alpine tends to be more bassie in their lower levels than in their high range HU's. Mid price range I've prefered Eclipse, Pioneer and some Kenwoods. High end HU's Pioneer and Alpine have been tops for a while.
life is too short to have any regrets