Well, now you can find out.
Roger Federer recently visited the Zurich office of longtime sponsor Credit Suisse, spending the day wandering the halls, signing autographs, giving a revealing, one-hour interview and even hitting some serves in what looked like a serve simulator. Of course, he had to keep pushing until he set the record for serve speed. (Spoiler: He later found out that someone else had already broken it.)
Some Federer comments from the video (via a translator):
• "It was important for me to seek and also find normal human contact, and it's been great having lunch here at the Uetlihof [Credit Suisse's complex] today."
• "A lot of things frighten me. Spiders I could do without. In fact, there are plenty of pests I can do without. Also, when I was at Disney World with my kids, for example, I was glad I only had to go on the little roller coasters and not the big ones. I don't think I could stomach that. Skydiving, bungee jumping, no way, not for me." • "Well, you certainly don't get much of a private life, that's one disadvantage [of being famous]. The nice thing, of course, is that people are always pleased to see you and you receive a lot of support. Many people also come up to me and say how great it is to meet me. That obviously gives you a really nice feeling. Amongst all the stress and in such a surreal world in the big cities and permanently on the road and all the pressure that builds up, it's important to remember why I actually play tennis."