Users wanting an alternative option to Adobe Photoshop, which doesnt have any current plans to fork PS to linux, can use GIMP in single window mode. Its easy to do, and much easier to use!
The PPA makes it easy to install the single window mode. Its addictive once installed. Heres how...
Open a terminal and type:
sudo apt-add-repository ppa:matthaeus123/mrw-gimp-svn
press enter and it will ask for password. then in the terminal type:
sudo apt-get update
This should update GIMP now. If it doesnt update, try running Update Manager in "System > Administration". Once GIMP is updated, open GIMP and you will need to click on "Window" on the GIMP menu bar, then select "Single Window Mode". Thats it! These instructions should work fine for recent versions of Ubuntu.
Its addictive once installed :)