I have the 18-200 which I think is similar in terms of performance.
Good points:
Very light and compact - ideal 'travel' lens or if you're in an environment where lens-swapping is a bad idea.
Acceptably sharp at f/8 and above. (I've had photos taken with it published on A4 magazine covers.)
Decent build quality.
Bad points:
Max aperture f/6.3 at 200mm, so needs good light or higher ISO.
Rather noisy focus - though quite quick.
No ring motor, so no full-time focusing.
Not as sharp as good lenses with a smaller range, but can be corrected with a little USM.
Range is actually 17-175, not 18-200.
Overall:
Very useful and recommended for those situations where you can't carry a bag of lenses or don't want to keep swapping.