what do you need it for? general walk-about? 18-55 is very up to the job.
sharper pix? get a good prime lens. the new DA35 is very good.
constant aperture? tamron 17-50. affordable and sharp.
my experience with superzooms had always been rather disappointing. u end up with long focal length u seldom use, max aperture that's too slow to be truly versatile at the long end even if u do, and so-so image quality at both the extreme wide and long ends.
the main reason some pple get a superzoom is sheer convenience: go on family outings or holidays, just wanna quickly zoom, compose and shoot. don't really mind if its not so sharp and find the slight barrel and pin-cushion distortion acceptable, just want happy pix for memories.
nothing wrong with that. but your expectations are important here. if u end up disappointed with the pix produced, its too late. the moment is gone forever.
u really want an affordable medium zoom, consider the DAL 50-200 or DAL 55-300. they're cheaper, they will allow you to experiment with shooting at 200 or 300mm and the IQ is good.
i've tried 18-55, 28-200 and 18-125 before... my walkabout lens now is the DA*16-50 F2.8 which i will definitely keep for a long time. ultimately, its about knowing what kind of pictures u want to take and getting the right tools to take them.