I've met and trained with lots of up and comers. But the two biggest I have met are Matt Hughes and GSP. GSP is exactly what you would expect. Very, very cool guy and very down to earth. He gave a seminar at our gym and rolled with us for a couple hours afterword. Oh, and he is strong as a freakin oxe!! He was a very likeable guy and went way above and beyond to answer everyone's questions and generally acted like he was happy to be there.
Matt Hughes on the other hand . . . one of the rudest, most obnoxiuos men I have ever met in my entire life. I have nothing good to say about this guy. He was just a tool, period. He came to a local show as a guest referee for the pro fights on the card. Before hand he set up his table out front with all his shirts, etc, and was sitting there signing autographs. My wife and I waited in line for an hour to buy a shirt and get it autographed. When my wife got up to him, she asked some standard question about being the champ (he was still the champ at the time). He literally looked at her, rolled his eyes, signed her shirt and tossed it back to her. Even though he could kick my butt, I felt I needed to repeat the question to him, giving him the benefit of the doubt. When I did, he looked at me and said, "I heard what she said". So I said a few choice words to him, albeit under my breath!! That night my buddy was fighting. He has this thing where he walks to the ring wearing these Elvis looking sunglasses. When he stepped in the ring, Matt literally took them off his face and threw them over the top of the cage and said, "Get that sh*t out of here". Then later that night, after the fights, everyone went to a local bar and grille type place to eat. We didn't even know that Hughes would be there, but when we walked in there he was. One of our other friends didn't get a chance to meet him, so he went up to him and politely asked if he would pose for a picture. He agreed. When he stood up to take the picture, my buddy asked in a joking way if he could stand behind him and pretend to get him in a rear naked choke for the picture. HUGHES FLIPPED!!!! He started yelling at my friend saying nobody gets him in a rear naked choke and was just blasting this guy at the top of his lungs. It was such a shame because this guy was the biggest Hughes fan you could ever meet. The look on this guys face is something I will never forget. He was devastated that his idol was such a jerk. Hughes is a tool.