They will heat the water enough to scold !!!!
In terms of having any problems - with the heater none at all.
I've had a slight issue with a higher flow rate ( which I consider due to the extra flex in the hose because of the heat, and therefore more water at the start of turning on the flow). If you run a higher flow, then this won't really be an issue.
I've just fitted a low flow rate micro switch ( which turns the heater on at a much lower water flow rate) to hopefully be able to control the flow from my pole tap, whilst still having the heater fired up.
The cleaning power of hot/warm water is very impressive.
Hope this helps.