u will be fine.. im 6'4" and i rode John aka Composimo's msx125.. John is 6ft and he rode the hell out of it recently on our Hillbilly Ride.. for me.. the stock bars would need to be changed or moved forward maybe.. and the shifter might need to be a little longer or i will just have to get used to it.. but other then that.. it rode fine..
John has a thread comparing the grom with a madass and ruckus.. not sure if he has it on this forum but i have seen it on totalruckus and another grom forum.. here is the link..
I've been wondering the same thing. The ergos can be set up for a range of riders, though, and changing the bars and controls can help. Some bigger bikes are uncomfortable for taller riders. I'm 6'2". I found the old Nighthawk 750 was too small to be comfortable. The CBR 900 series was excellent--- but the tank bulges hit just at the insides of my knees! (On my wife's scooter I have to sit on the passenger seat to get my knees inside the fairing!) At least the Grom looks like it's possible to set up.