I used the 70-200 f4 IS USM lens with the 1.4 extender until I had to have more reach, then I got the 100-400 L which I like very much. The 100 f2.8 IS Macro is a good choice for portraits,flowers and Macro shots. For landscape I might go for the 16-35 f2.8 and use it with a tripod. I don't shoot many Landscapes so my 17-85 fills that part of my kit shooting HDR until it breaks. Sometimes I turn off IS for panning shots and really miss it when i forget to turn it back on.