To add my bit to this as my name has been mentioned, the main difference with my experience at organised events, is that as Col has indicated, I go out of my way to be respectful to others taking part in the events, and hills aside, I always ensure that I am riding at a comparative pace to regular mtb riders, will frequently even hang back slightly, and use no assist at all when possible.
In respect of hills, I use as little assistance as possible, and again try not to ride at a speed that will draw negative attention. If I'm riding with another mtb rider, I don't ever find that I need more than eco mode, and it's fairly rare that I'd use tour mode, let alone sport or turbo.
I'm not saying that any riders of bikes fitted with dongles wouldn't do the same, but what is the purpose of a dongle, if it isn't to create a bike that is free to travel at a faster rate.
To put it into some kind of perspective, I can get between 35-40 miles out of a battery charge at an event, and as SRS will testify, I have arrived back with half of the battery level remaining. If I ride on my own around here, I can struggle to get 20 miles from a single battery charge. So my use of pedal assist is far less at organised events.
At an event that William Tell happened to be at on his Haibike last year, he was happy to use sport and turbo for the ride and used two batteries for the ride. That was the same event that I returned after having only used half of one battery. This example of Williams use, is purely to show how much effort that I am putting in with the riding, rather than just letting the bike do all of the work, and the associated possibility of the e-mtb advantage being pronounced more than it needs to be.
I do fear and know from having spent time talking to event organisers that my days are potentially numbered. The sole reason being bikes fitted with dongles, or the possibility of. The financial and legal risk that event organisers face because of dongles, or the possibility of dongles being fitted, is too great for them to ignore. 
I know that sooner or later, I am going to be told no more riding. As it is already, I try to loose myself in the middle of the group to avoid attention, and pretty much hide. It shouldn't be like that.
I have also just been given sole access rights to 500 acres of privately owned woodland, that has no public access rights/no rights of way what so ever and is fully fenced in. I'm also in negotiation to gain permission to use a further 500 acres next door to this land, and again it has no public rights of way or permitted access. Both sites are set either side of a valley, and could be considered perfect for a bike with a dongle.
This however holds zero interest to me, as I just don't see the point, or even the fascination of using a bike fitted with a dongle, or an s-pedelec in an off road situation. You might just as well be riding a motorbike.
I can't say that I feel the same on the road though, and find the cut off point quite annoying at times. But that is just me being lazy, and I just remind myself to be grateful for any assistance.
