Help finding a lens for my T1i/500D please! =)
Going back to the OP's original question, another single lens option would be the Tamron 18-270 or the Sigma 18-250 - either would give you the extra range you want. As others have pointed out, there will be a sacrifice in quality compared to the best lenses, but still you'll be able to get very good images and have the convenience that you want.
There is nothing wrong with making the choice of a single lens for your slr - in fact superzooms are very popular because of their convenience.