So I went to the Toronto TMS last week and had a blast. I was lucky enough to see Rafa practicing on two different occasions, first w/ Carlos Moya, and second with David Nalbandian.
The first practice, with Moya was fun to watch, however, neither player was fully relaxed as they had to stay focused and serious for their first round matches. Nadal arrived five minutes late and Moya teased him about it. Moya played some soccer with his coach while Nadal changed his shoes. Two seconds after Nadal got ready his coach and uncle Toni came running in and Nadal started teasing him about being late. Toni gave Nadal a blue cap and Nadal responded by smiling and giving him a buddy tap on the back. After this, the Spaniards hit for about an hour and had to leave very quickly because there was going to be a match on the court they were on.
The second practice I watched was a lot more fun as both Nadal and Nalbandian had already lost their first round matches and were much more relaxed. The two were goofing off a lot, at one point, when they were playing points, Nadal hit a stellar volley to which he said laughingly, "Esa volea me acuerda de Sampras" (this volley reminds me of Sampras. Then, when he tried to do it again and missed badly, Nalbandian asked teasingly, "Y esa?" (how about this one?). And Nadal replied laughing out loud, "esa de Nadal!" (this one [reminds me] of Nadal)
I also noticed that Nadal is the only player who signs autographs during as well as after practice. He likes to talk a lot and is very polite. If you speak to him in Spanish he will very likely have a conversation with you. I talked to him and to David and they were both very nice.
Anyways, I hope this helps you guys have an idea of what Nadal is like.