This is a very old argument. However, there are only so many hours in a day. I use Gimp occasionally but I bought Photoshop because there are more tutorials, blogs, and resources in general. I'm a developer and weekend warrior with graphics. If the apps are too different, I only have time to learn one.
For Gimp to really hit the main stream, it should make it trivial to switch between it and Photoshop.
For Gimp to really hit the main stream, it should make it trivial to switch between it and Photoshop.