Andy Ihnatko took a bunch of pictures using an iPhone 3GS, Nexus One and a Nikon D200. Of course the Nikon D200 took the best of the three. The iPhone 3GS took photos that were usable in all lighting conditions, including fairly dark environments. The Nexus One took much better pictures than the iPhone 3GS when there was plenty of non-tricky lighting but when lighting was not ideal neither were the pictures it took.
I would have loved to have seen a comparison of something in between the smartphones and the pro-level DSLR. Say, for instance, a Canon S90. I have been using a S90 for about a month and I think it is good enough for almost any situation. (Almost because the autofocus and shutter speeds are too slow for fast moving objects.) It is a prosumer-level compact camera that takes wonderful pictures, which are much better than either the Nexus One or the iPhone 3GS in any lighting condition. And in my non-professional opinion bumps up against the quality of the Nikon D200. Importantly, the S90 is really pocketable. Yes, it is an extra device to carry around in addition to your iPhone 3GS or Nexus One, but trust me, you’ll forget you’re carrying it around (unless you like to wear tight pants) until you need to take a picture. And at that point you will be quite glad to have such a capable but oh so pocketable compact camera.