The Tempra 24 Plus has exceeded expectations. It does require 2 separate 6/2, 240v circuits with a 50 Amp breaker per circuit. If you're replacing a hot water tank, the existing 10/2 wiring is not adequate. If you do not have the proper knowledge to safely install the needed circuits, the cost of installation will need to be added into the final cost.
I found that the default temperature of 115°F was a little cool for everyone's liking, but 120°F made everyone happy.
We can all take showers one after another, do dishes, run a bath if wanted, and we've actually done all 3 at the same time without issues.
I expect long term reliability to be excellent, as Stiebel Eltron is the original developer of tankless whole home hot water systems.