Do you need all that range? I'd urge you to reconsider. Once you discover its shortcomings as a superzoom, you'll feel the need for a constant large aperture lens. For your budget, the Tamron 17-50 f/2.8 is easily within range. On a 1000D body, this range is the most commonly found walkabout range, for wide angle work at 17mm, and some portraiture or closeups at 50mm.
I personally uses the Canon EFS 18-200mm lens and find it handy.
The IQ of the lens when compared with L lens or standard telephoto lens is not that bad really. I find it pretty decent IMO and basically only needs some slight sharpening for the pictures. An all rounder lens for walkabout shooting, saving the time and effort for changing lens.
However, if TS wants to do serious Macro shots, please do consider the Macro lens instead.
If you want some reference pictures, you can visit my flickr and view the newbie pictures which I took with the 18-200mm lens on Canon EOS 450D.