I carried both my Droid X and my iPhone 4 today and shot some casual photos and videos in various lighting situations. My experiences did not break new ground relative to the review at ArsTechnica.
The Droid X has significant shutter lag when compared to the iPhone 4. It is also slower to focus, does not handle low light as well, and has strange halos when the scene is very contrasty.
When shooting an action shot of diving, even in good light, the Droid X shows distortion related the rolling shutter that it uses. The iPhone did not show any distortion in good outdoor light, even on action shots.
Video looked ok on camera in the Droid X, but unfortunately, Phanfare does not properly convert the 3gp video files that the Droid X produces so I can’t compare on the web.
Overall, the photography experience was a step back relative to the iPhone but probably about average for a typical cell phone. I have posted all the photos and videos for your perusal. The iPhone 4 photos were imported through the Phanfare app on the iPhone. The Droid X photos where brought in by saving to a dropbox account (dropbox.com) and then importing on my desktop via the web organizer.