I have the 70-200 F4 IS. It is a great lens for travel because of its sharpness, light weight, and range. It can produce nice bokeh focused to closer objects at the long end. The contrast is excellent.

The IS version is weather sealed unlike the non-IS
The IS version is generally sharper at most lengths and focal ratios.
It has IS (obviously) which is awfully nice for handholding with an F4 lens.
The IS version weighs only a little more.

As a travel lens, the 70-200 F4L IS USM is hard to beat.

You might also want to look into the 70-300 F4-5.6L IS USM too. It offers mostly similar performance but with 100mm more at the long end. It costs more, but is another great choice for a travel lens due to fairly light weight and compact dimensions for an L series lens.