It's also pretty smooth about searching. Plug in a zip, and go there. Plug in an address and zip, and go there. No separate fields, or wondering what to fill in. Again, it's just smooth.
And when you zoom in, rather than wait for it to pull down an image of the whole screen, it pulls down bits and pieces, from the center of the map outwards, (assuming, usually correctly, that you're more interested in the center than the edges).
Appearance-wise, it's really clean. It doesn't do most street names until you're in close enough for it to not be cluttered.
I've got an old, slow, 600MHz box, with a fast connection, and the speed moving things around was pretty decent. It pre-loads stuff off the edges of the map, so you're not waiting as much when you're moving around.
(Very minor nit: you can't search for a lat/long. So much for using it with my GPS. Ah, well.)
For the time being, though, I've found a replacement for MapQuest.