My original thought was to get a 70-200 f4 IS so I borrowed a friends sigma 70-200 and found most of my shots were at the long end. It worked out great at the zoo shooting wildlife but I found myself wanting a little more reach. Now I'm thinking a 200 f2.8 + 1.4TC or a 300 f4...then again the 100-400 is another option too....ah I'm so torn 

