The Tamron SP 15-30mm f/2.8 Di VC USD ($1,199) couldn't have been an easy lens to design. It covers an extremely wide angle of view, has a maximum f/2.8 aperture, zooms, and is optically stabilized to boot.
Sharp; Optically stabilized; Maximum f/2.8 aperture throughout zoom range; Integrated lens hood; Ultra-wide field of view; Close focus capability; Available for Canon, Nikon, and Sony systems
Lots of distortion; Bulky; No filter support; Some flare issues