I think it would have an effect - you control them by leaning your weight so any recoil would either - make the thing move or throw you off. I think that is probably why they are using small caliber weapons. There is a larger version of that photo and they all have pistols and small smgs except one who has a small caliber rifle.
I know you guys are kidding but I'm gonna be Mr Downer and talk about how I see the practicality of what they are doing.
Given the location/situation that they are using and implementing these - which is in Beijing for the Olympics for first response teams to terrorist or any other control they need. Consider trying to get First responder vehicles and SWAT trucks though Beijing during the Olympics... not very efficient - so whats better than running/biking there? Segway-ing there.. gets you there faster than car / running and less tired than the biking / running.