I had a glind.
Firstly, i only used it once because back then i was a bit of a grubby fawker when camping by myself or with mates. Generally unless it's over a 4 days i won't wash
but when i DID use it, what a magic little unit. Temperature was controlled via the demister temp controller in the car, as that controller varied the amount of flow going through the valve on the heater hoses. Even with a cold start on the 1HZ, it really didn't take long to get enough heat in the engine to start warming the water since -
A. The thermostat in the engine means that engine water is warmer than radiator water until it opens, and frankly, if you can stand in 72 degree water you're doing better than i.
and
B. Once the engine is at operating temp generally i only needed the demister set at 1/3 for it to very hot. So i'd start it at full hot and have the missus or mate turn it down a bit as the engine got warmer.
Some things i'd do different or same if i did it again -
1. I had quick connect air fittings hard mounted in the engine bay. Connect shower head, connect feed hose from Jerry can. Done. Do this.
2. I didn't have the pump hard mounted with a switch. Because the pump vibrates and jumps around i fashioned a cradle and rope for it that hung off the open bonnet. Between farking about with that, and setting up alligator clips, i just couldn't be farked. Don't do this. If you have the space to hard mount it with a switch do that instead. You'll definately use that more
3. I simply could not be farked setting up a shower tent. I just kept a plastic or rubber perforated matt in the car/trailer and stood on that so i didn't get muddy feet. 2 feet square is plenty. Do this
4. One jerry can is plenty for a shower. If you have a wife, make sure you have enough room for 32 jerry cans, or carry a hose long enough to reach the river.
3 bucks for a 4 minute shower in a caravan park eats massive horse doo doo. Just on principle i'd pay the set up costs for the Glind. Now that i'm older, and have a nagging wife, i'd definately consider it de rigeur on any touring vehicle i set up.
Hope this helps