There is no 'ideal' travel lens. Depends on what your priorities and expectations are.
I shoot with a D700 FX body to get better image quality, better dynamic range, better low light performance, and also to do justice to many FX and older lenses I have from the film (35mm) days.
I find the AF-S 14-24/f2.8 and the AF-S 70-200/f2.8 indispensible from travel (people and landscape). The UWA captures the awesome sceneries and landscapes. The 70-200 allows you to zoom in and capture the moods of local folks, etc. without intruding to close on them. For the mid range, I bring along a AF-S 50/1.4G that gives me extreme low light capabilities, shooting local dances and performances, etc. without flash. I always leave the standard 50mm on the camera and try to really use this lens well. This prime lens is usually very sharp from anywhere from f2.8 to f11.
On some trips, I replace the 50mm prime with the AF-S 24-7-/2.8 which then stays on the camera most of the time.
You're welcome to check out my flickr photo set to see some shots taken during my recent trip to Turkey using the combination of 14-24, 50, 70-200 lenses.
http://www.flickr.com/photos/28858702@N07/sets/72157625532446002/
Choosing one lens to cover the entire range will naturally have some trade offs, i.e. lens speed (smaller apertures), and greater distortion (since the lenses are required to zoom over such a huge range of focal lengths), sharpness and contrast.
Happy shooting.
Fred