I have a propane fired water heater. (
Rinnai )
This works very well, and is OK for a shower. One slight drawback is that instantaneous heat is only available provided you keep the pilot light burning, but ignition is very simple (just push a button). I use 3/8" copper pipe to run hot water to other side of my cat, (was originally 3/4 plastic pipe) and that reduces wasteage of cold water.
Gas installation laws in UK have recently made installation of these much more difficult, but that beats blowing up