As a web-Dev, I must disagree. For the logos, backgrounds, textures and whatnot I am called to deal with, GIMP is perfectly adequate for the task. In fact since I work with Drupal hosted on Debian/LAMP servers, I dig on Ubuntu as the Power-Client (free!) because the OS is so similar when I work for clients (actual, paying clients).
What is not cool is having to stop work and having to ask the client paying for my time, to also fund a Photoshop purchase (even Elements which costs $/euro 100 at the local office supply store, but this takes time folks). Since Ubuntu offers GIMP along with native SSH/SFTP, (etc., etc.) I'm ready to work, and get paid.
And of course VMs run really well on a project too, and are extremely portable across hardware workstations, with excellent Developer snapshot facilities, but I digress.