I agree that the Crystal Harmony inside cabins are excellent. I was very pleased with my inside cabin on this ship. The closet space is not particularly great, but I counted 17 drawers of storage space in my cabin! Also, the location of these cabins is good. I am sailing on the Harmony again this August (although I paid a little extra this time for a cabin with two portholes). I highly recommend the Crystal Harmony.
I also did a Harmony inside and enjoyed it - the amenities (like down comforters and superbs sheets, etc) made up for lack of window. Also, I find that the only time I want to be in my cabin during the day is to take a nap - very easy in the darker, windowless cabins.
Our only Crystal cruise was an inside cabin on the Harmony. It was how we were able to get a great price and still enjoy all those amenities like excelent food and service. The only thing we had a problem with was taking a shower in those tubs. As I mentioned elsewhere, the tubs are elegant but they are not easy to get in and out of. Unfortunately my wife had taken a fall about 4 months before this trip and still needed help (afraid of falling again) getting in and out of the tub for a shower. It was some feat for the both of us, not being the slimmest people in the world, to maneauver in that inside bathroom to accomplish this, especially with the door opening inward.