Right now im using 18-200, but will be switching to 17-55 and 70-200. Im also contemplating the need for 12-24. The thing is that now i tend to think that i dont. For really wide creative shots ive got 10.5mm fisheye. 18mm is mostly wide enough for normal use. Usually i find i need wider view for landscapes/cityscapes. But you can always take a few pics and stitch them into panorama. You can even do it for moving subjects! Just take central pic of the subject, wait till it goes away and take other pics for pano. There are obviously advantages and disadvantages to both approaches, but 12-24 aint cheap and it bugs me to change lenses. What do you think?