Mcgregor has never fought more than five rounds in ufc rules, how will he survive in a sport which is more physically demanding.
Even if mayweather lets mcgregor hit him or show off his defence, it will still suck, just look at the andre berto fight, a disaster waiting to happen, mayweather was toying with him on the ropes and even with that the fight still sucked.
EDIT: Then you see these type of BS:
http://www.boxingscene.com/white-mayweather-mcgregor-bigger-mayweather-pacquiao--117545as if fight fans will buy this fight thinking its going to be better than may vs pac, which was the only most wanted fight both boxers, both #1.

“Yes, of course,” Ellerbe said. “Why not? You’ve gotta understand, obviously with Mayweather-Pacquiao, and Stephen can attest to this, that was a fight that the fans had been talking about for years. There’s not one place that I go to, that Floyd goes to, that anybody affiliated or associated with Floyd Mayweather [goes to], that [we don’t get] asked the question, ‘Floyd, are you gonna fight Conor McGregor?’ This is a very, very hot fight and this is a fight that the fans want. It’s gonna be a tremendous event. The fans wanted this fight."
Even the promo to this fight is bs especially when it comes from people who fail at hyping it up. A quote from dana white:
'Floyd Mayweather is 40 years old, he's always had problems with southpaws. Conor McGregor is 27 and he is a southpaw. Whenever Conor hits people, they fall.
The more I see of this the more I hate this fight.