I freeze it all the time. I usually make it, then freeze before baking. When I thaw it out, I add a little milk to the dish, then bake it as usual. The milk magically absorbs in the oven.
Sometimes, if I have leftovers that have already been baked, I'll freeze it,too. The texture isn't quite as nice, but as long as you do the same trick (add milk to the dish as you heat it), it is good enough. My kids certainly don't complain.
oh, fwiw, I make it with a bechamel based cheese sauce