My parents have in their new extension. It is nice.
If we get the house we're after we're going to start renovating and extending immediately and the current kitchen will be ripped out, with underfloor heating being installed.
I've got it put in our extension and living room. I had reservations to start with, but wouldn't be without it now.
If we hadn't already spent a fortune at the front of the house, I'd have run it all the way through.