I like Safari for its integrated dictionary look-up (CMD-CTRL-D) and its handling of RSS.

The dictionary function, about which I had no clue, is sweet. Apple never fails to amaze me with the key combo functions that they've implemented very quietly on the side. I loved Safari's RSS handling until the number of feeds and my habit of checking them all at once made that untenable. I think that issue comes down to how you use RSS, and how much.

Props to Quicksilver, all the way. It's the only application that's permanently open on my system now. Well, that and the Dashboard which I can't turn off.