Yeah, I'm worried about the water temp too. I wonder if the whole business end could be dunked into hot water for a pre-heat?
How many shots is one cannister supposed to do? Cost of one cannister? Cost per shot merely for the pressure?
How about a mashup of the two? It'd be interesting if someone would create a handle that could work with either a pump OR a cannister, and a business end whose thermal properties would be something to write home about.
Then add a built-in grinder and steaming wand . . .