Actually at household water pressures, water's boiling point is somewhere from 140-160°C, so it's actually somewhat plausible. I'm sure some less heat tolerant stuff would have to be upgraded, but the system's total pressure would be about the same (with the added danger that the consequence of a pressure failure would be a steam explosion instead of a leak).

And of course turning your faucet on hot would now blast out a stream of boiling water propelled by superheated steam, which is probably less than ideal.

This is the only correct answer. I never said "degrees" anywhere, so it's obviously Kelvin!