I have the opportunity to purchase this lens for $280. I am thinking of having this as my "walk around" lens for the 50D I am picking up tomorrow. I already have the nifty fifty. What do you think, is it worth it for the price? ( I have read differing reviews on the EF-S 17-85mm f/4-5.6 IS USM) It is also about all I have left in my budget for the near future.