If you don't know what to use a 17-35 for, don't buy it....once you'll notice the limitations of your 28-80 go for either 17-35 or 80-200, or both ;) They'll be a nice addition for the more experienced photographer and even then a good 28-80 that's big and sharp will be of most use. Especially when doing mixed photography, it's a nice compromise between the longer and shorter lenses (cause with some cheating the 28 is okay for semi-wide angle shots and the 80 is okay for longer shots). So I reccomend getting a good 28-80 lens first of all.