I multi-task at work all day long: I flip between two computers, with multiple programs open on both computers, and I'm responsible for answering a variety of telephone lines ... all for different things (boardroom bookings, facility management, service calls, parking calls ...), and people will come into the office to pay for things or ask for parking passes, and then I have to use the walkie-talkies (I get a real kick out of saying "10-4"), and ... Heck, I'm multi-tasking right now -- since I started typing this message, I've had four phone calls, three walk-in customers, an email from a manager and a brief chat on the walkie-talkie with one of the servicemen. Whew!
When I go home at the end of the day, I do one thing at a time. I'm proud of how well I multi-task, but I enjoy focusing on one thing at a time to the exclusion of all else. Sure, I can watch TV, listen to music, play on a computer and read a book all at the same time ... but I don't wanna! :P I want to enjoy the television program I'm watching, I want to focus on the computer game, and I want to escape into my book. Listening to music is the only thing I try to do while doing other things (except watch TV).
My fiance, on the other hand, is absolutely incapable of multi-tasking (except for the TV ... he can have the TV on regardless of what he's doing: reading a book, listening to music, having an in-depth conversation with friends, doing advanced math ...). Fortunately, his job doesn't require it. He focuses on one thing and does that very well, and then he moves on to the next thing. He gets flustered if he has to switch from doing one thing to another, and it annoys him when he has to leave things unfinished. He can be extremely single-minded at times.
So, I don't think multi-tasking is a bad thing -- it's often very necessary -- but it isn't something I enjoy. I'd rather devote my time to one thing and be sure I've done that one thing well, and then start something new. Unfortunately, I seldom have the luxury.