Do you mind changing lenses? Sony zoom 18-135mm or 18-250mm or CZ16-80 or CZ24-70

I am interested to know whether you are happy to frequently change lenses, or whether you would prefer to mainly use a "super" zoom lens, such as the Sony 18:250mm, the Sony 18:135mm, or the Tamron 18-270mm lens with your Sony A55, 57, 77 etc.

For travel photography and general use, I bought the Sony 18-250mm lens to go with my Sony A55 and I'm quite impressed with the results. I also own a CZ24-70mm and a Sony 70-300G for use on my Sony A900, but I seldom use these on the A55 because I would need to be changing lenses frequently! This is because I enjoy both wide angle photography (for landscapes) and also telephoto photography for birds etc.

A friend is buying the A57 and has told me about a really good deal if you buy the A57 with the "kit lens" Sony 18-135mm.

It seems that this lens may have as good an optical quality (if not slightly better) than the 18-250mm lens. Is this correct, do you think the 18-135mm lens is a good investment?

Or would you prefer to change lenses more often and go with "lesser zoom" lenses, such as the CZ24-70, or the CZ16-80 lenses (or even a prime)?

I fully understand that a lens such as the CZ16-80 or the CZ24-70 will produce better image quality than the Sony 18-250mm lens, but do you consider the effort of carrying an extra lens and frequently changing lenses really worth it in terms of the image quality gained with APS-C cameras? It seems to me that such image quality gain is sometimes only visible with larger print sizes (perhaps 15 inches wide plus).

Cheers

Rob

http://www.robsphotography.co.nz/seal-1.html

Example of an image captured with the A55 and the Sony 18-250 lens: Fur seal "invades" popular New Zealand walking track "The Camborne Walkway"