I'm strongly considering this wide angle lens for my trip out west (Montana). I'm going to see my dad and bro and want to take massive wide angle landscape shots and potential other creative exposures. I have a 1.6 Fovcf or Canon 50d and my current lens setup is 28-135 kit, 50mm 1.8 prime, and 70-200 F4L USM. Roger on lens rentals says it is a great lens but just want get some other feedback on it. Is it worth the $699?