What do you shoot?
I'm a Canon shooter, but I've always drooled a little over the 18-200/3.5-5.6 with VR. Seems like a nice, solid, does absolutely everything lens. I'm a wide angle fan, so that paired with a nice ultra wide like the 10-24 would be tits.
Although Canon now makes the EFS 18-200/3.5-5.6 IS as well. Haven't heard if it is as good as the Nikon or not.
Sadly I have no experience with either. My EFS 10-22 practically never leaves my camera.