Hi,
That is what they are good at, going up hills, and into strong headwinds.
But given they shut off at 15mph I've had no problems going past them
on the flat, though downhill the extra weight should help for more speed,
but not really, as hardly any have proper gears for going downhill.
TBH if they could do 20mph before shutting off (pedal assisted or
not) they would be lot more interesting to committed cyclists.
There is a world of difference between 15mph and 20mph.
In their favour though is whilst you can't go fast easily,
they are great at preventing you going slowly, and
take all the effort out of setting off from a stop.
Conversely one could argue you can go faster overall
on a normal bike and generally an electric bike prevents
the development of the fitness needed for a normal bike.
Personally, whilst its still possible I'll struggle up the hills.
rgds, sreten.