Best zoom for light weight travel?

Playapixie wrote:

If you could only cary one zoom for travel, what would it be?

I have a GF1 and am trying to decide which single zoom best meets my needs for travel. I travel very light weight and size/weight of gear is a strong consideration.

I used to have the Panasonic 14-140. I traveled SE Asia with it and then sold it. In retrospect, maybe I should have kept it. Image quality was very nice, but size/weight were an issue, so I thought I'd try something smaller.

I then bought the Panasonic 14-42 compact/retracting lens and took it on a trip to Spain. Everything about this lens is unsatisfactory except the size. Not sharp, dull contrast and colors, and the lever for zooming feels just wrong. I plan to sell this.

My travel lens dream list:

-compact and light

-punchy, sharp images

-fast (would love 2.8 or faster)

-good zoom range (does not need to be wide, as I also have the 14mm 2.5 and 20mm 1.7)