I actually do. For years I didn't realize the capabilities it has.
I used to use Graphic Converter and PS, but lost them both on the laptop when I upgraded to ML. I bought Pixelmator, but really haven't used it much. I have Aperture too, really like it and use it for more intensive editing (or nice pix I want to print).
But for basic color enhancement, cropping or resizing especially to the web, I'll use Preview.
I discovered if I select, then copy and Apple-N for new, I don't even have to paste my selection.
I have iPhoto 11 I think, and really only use it for calendar creation. The calendar app prints way too small for me to read when it's on my cork board.