We have a CR38 with a dedicated spot just aft of the sink and outboard near the hull. It is rather like an open extension of the small storage cupboards behind the sink.
We just use a cheap $40 microwave from Sam's Club but to tell you the truth we don't use it much. Both myself and my wife love to cook and just can't think of much that we would like to nuke (at least food-wise
At one point the original microwave gave up the ghost and we didn't bother to replace it for months. We actually liked having the extra bit of storage space!
Hope this helps,