My prior post suggested using the 18-200mm zoom with the Sony NEX 5N as a great travel camera combo. The lens is a beast, however, overwhelming the lithe camera body; although convenient when not wishing to swap lenses, is so huge it defeats the purpose of a small SLR-quality travel camera.
And for those of you who miss the viewfinder, you can buy an add-on viewfinder for the 5n, or move up to the NEX 7, which has a built-in viewfinder. (The 7 is currently unavailable due to supply problems, but production out of Thailand is ramping up again.) The 7 is much more expensive than the 5n, and reviews have been mixed for the extra cost. I prefer the 5n and the kit lens plus the 55-210 zoom.
More lenses are coming out, including some really compact ones like a rumored 30mm f2, which would behave like a classic 50mm lens. (The APS-C sensor of the NEX line has a 1.6 multiplier, so a 30mm lens acts like a 50mm lens on a full-frame sensor.) That would be a great walkabout lens, very fast and easy to use for most situations.