Personally I hate IE, and for the last 4 years or so have been using Firefox, until yesterday when I started using Opera.
In terms of looks and fluidness I prefer Opera, in fact my only complaint is the lack of a home button on the back/forward/refresh toolbar, but I am getting used to it. Oh yeah, the way Opera opens the last page you were viewing before you closed it... not good if I happened to be looking at something my Ma would rather I didn't see.
Loading times? I noticed no significant difference between Opera and Firefox (I've forgotten what IE is like).
Spyware. Now, I haven't checked his out myself, but a good friend of mine has "performed an experiment" over a month to see how much spyware he gets on IE and Firefox. He says that there's only a small difference between Firefox and IE. He says. Meh.
So what takes the prize for you? Oh yeah, for me it must be Firefox, although Opera is quickly growing on me.
EDIT: I had the idea for this thread while soaking in the bath last night. As you do. Maybe we could make it an annual thing?