Anyone swapped water heater for a Tankless On-Demand?

Boatycall wrote:
I've read where the first gen RV tank-less water heaters had issues, a lot of second gens seem to have addressed the issues. Things like not creating enough temp rise for a given flow for a shower, reliability, etc.

I'm looking at this one, Girard Tankless RV Water Heater .

Front cover is sold separately to accommodate various colors and Mfg's of existing water heaters.

Thoughts?
Save fuel or use more?