1. The 18-55 IS kit is really good sharp..
I got a A16 (17-50 f2.8) and the only good about it is the f2.8... sharpness wise the kit lens are as good as it...
2. Don't know about the 18-200 yet... hope its as good.
But for the US$500 different.. you can get a US$250 55-250IS... and may be an external flash (important for model shots).. or a Ultra wide if you into outside shots...
so it come downs to what your needs going to be.
Try to look out what tele end of img will gives you..
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BTW, Tamron 18-270 also coming.. (it has 70mm more... not that you may need it..., one more direction (diagonal) "IS" than Canon... not sure any better... and price about US$100 less... it may be wise to check that out too...)