18-135IS, who shoul I believe?

I'm looking for a travel lens.

I have very good lenses (17-55 2.8IS, 70-200 F4L IS, 10-22, 300mm F4L, 400mm F5.6L, 50mm 1.8 and the 18-55 IS)

None of these seem to be good travel options. I'm traveling now and have the 50mm as well as the 10-22. Not very versatile.

I've had bad experiences with Sigma 18-200, and Canon 18-200 is too big for my taste.

I'm thinking of a generic lens like the 18-135 to pair with the 50mm 1.8 (for night pictures and portraits, which is what I like best).

For me fast/accurate focus is probably more important than pure image quality.

Some say it's crap, Bob Atkins says it's great. Who should I believe?

Thanks