I'm bilingual, rather than multilingual, but I'll answer mrsd's questions anyway.
1. Do you dream in your primary language? Or all of them? I dream in both English and German, roughly 50/50; I actually woke up in (German) recovery rooms following three surgeries speaking German - I hadn't expected that (I asked).
2. How do you keep the other languages 'fresh', when the people you are around DON'T speak French or conversational Chinese. I still read Spanish newspapers, but my Spanish is by no means "fresh".
3. If you have children, do you speak to them in all those different languages? No kids, but I speak both German and English with my eldest nephew. He would always answer me in German when he was little, but now he really wants to work on his English, so he even emails me in English. Friends here (he's Swedish, she's Costa Rican) raised their two kids using four languages; they alternated days of Swedish, Spanish, English and German. The kids are in their twenties, and I've never heard them "mix" their languages.
4. Do you feel you have a 'gift' for languages? That is, was it easy for you to pick the languages up? (Or could anyone do this?) No, I don't have a gift for them at all, though that might be due to my hearing. I have a "feel" for written language, if that makes sense. For example, we were on vacation in Belgium a few years ago, and I was worried beforehand that we would have trouble with Flemish. My husband did, I didn't. Once I picked up a newspaper and realized that I understood 85% of what was written, I lost my fear, and started talking to people in a mixture of English and German. It worked! I don't speak Hungarian, but I'm the one who reads the menus, traffic signs, etc., not my husband, who does speak some. My in-laws, who are Hungarian speakers, find that hysterical.
5. What language do you find the most beautiful on the ears? I'd go for a Romance language - Spanish, French, Italian, or Romanian.
6. What made you interested in all the languages in the first place? I guess having a multilingual father helped, and a mother who studied Latin (so I was exempt), but I had "Fernweh"/wanderlust even as a kid.
7. How did you learn? Tapes? Schooling? Immersion? Schooling and immersion. You don't learn words like "fuse" or "knockkneed" at school.