This compact lens is a very good travel companion, light and reasonably sharp at all zoom settings and apertures.
At least in my own sample sports the best results at the wide angle end, while at 85mm is softer.
First row 24mm, left center, right borders; second row 85mm, left center, right borders (on Canon 5D Mark II):
Like other zoom lenses if you try to correct focus in camera you have to choose a specific focal, because the amount of correction needed is vastly different from wide angle to tele.
Not a great lens by any mean, but a great value for the price. And it will be light on your neck.