Saw few questions on whether to change a better len..so my question will be "does buying a really good lens make that big a difference in sharpness? Definitely!"
Few years ago when i was starting DSRL and like the other biginners was using the kit len 18-55 (without IS somemore). I had been shooting with this for years, and in one day, afterseeing what a difference a really sharp lens made on 17-55mm F/2.8, I wouldn't shoot with my old lens again. We all know that gd len not cheap, but like anything else in photography (and in life), the really good stuff costs more.
So, if you're thinking of buying a normal zoom lens, sharpness clearly isn't your biggest
priority. A quality lens is an investment, and as long as you take decent care of it, it will give
you crystal clear photos that inexpensive lenses just can't deliver.