Ok I have been using the 18-135mm and it is a fairly good starter lens, but i have noticed the the edges get a bit darker specially when you have got blue sky in the pics. You can crop it out and looks good.

I have tried out the 24-105mm and it is a very nice lens. My wife is off to Singapore next week so i might get the lens over there as i can get it for $960. It is a grey lens but i can send it back to my friends over there if it breaks which i would not think it would being an L.

Cheers.