For a while I've been happy about my lens setup for my DigitalSLR: a Sigma 18-200 as a general on-camera lens, Canon 10-22 for wide, Canon 50 f1.8 and 100 f2 for low light portraits and narrow depth of field. It's a good set up that's helped me take lots of photos that I like.
But, as most obsessive amateurs like me know, there's always that nagging desire for better equipment. I hear about how a consumer-grade lens like the 18-200 can't be as sharp as something a bit better, that I can get a lens that will auto-focus faster and quieter, maybe my longer tele shots are a bit softer than I think I ought to be able to get?
The counter is that most photos only end up on my own screensaver with a resolution that is way less that what my camera sensor will dish up. Having one lens to cover such a big range is very convenient, especially when walking around with someone else who I don't want to slow down with lens changes.
But finally the new-lens demons began to gain control. I was vacillating in two directions. One was to get a better quality mid-range zoom - specifically the Canon 15-85. The other was to go for a better quality telephoto. The argument for the mid-range is that would replace the 18-200 for most of its shots, giving me better quality overall. The fact that it goes wider means I'd have less need to carry the 10-22 with me. (Although that's really a disadvantage since I like using the 10-22.)
So far I'm happy with it. It's a bit longer than the 18-200 and bit lighter. It handles well and auto-focuses really fast. I think I am getting some sharper tele pictures out of it, but that could easily be a rationalization.
The most interesting consequence to buying this lens is the change to my usual lens rig. Now I tend to go out with the 10-22 and the 70-300, swapping between the two lenses depending on need. I would think that this combo would leave me a big gap in the mid-range, but I find I'm not noticing it too much. I do carry the 50mm but rarely put it on. I can always take a shot at 22mm and crop it if I need to reframe the picture. (Cropping on the computer to adjust framing is one of the big changes to an ex-slide shooter like me.)
I'm still concerned about missing a shot because I'm reluctant to mess around with lenses when my companions are moving. To handle this circumstance I keep my CanonS90 in a handy pocket. I use it rarely, but am comforted by its presence.
I was expecting to get the 15-85 at some point, and the perceived better quality of some of the 70-300 shots should encourage me. But maybe I can hold out by enjoying my current rig, and digging out the 18-200 for when I really feel I need the convenience.
1: Although I've been pretty happy with this lens, if I were buying now, I'd go for the Canon 18-135 since it's rather smaller and lighter, for a minor loss in reach.