My buddy Pavel is has been coding this software, Pixel, for the last few years and in the last few months that we have been talking i have been extensivly testing and using his software as a replacement for photoshop, period.
This is something I started brushing up just for fun, dont know where its going but this is what i got so far.
The Software is still in beta testing versions, but is nearing a stable 1.0 
We will be trying to get sponsored so we can have a boot at siggraph to introduce the software to the graphics community.
It currently runs on:
Windows
Mac OS
Linux (x86,ppc, and others)
Solaris
Morph OS
SkyOS
Net BSD/FreeBSD
and other platforms as well.
Tablet support under linux is currently in development and i will be submitting bugs to accelerate the development of the program.
it currently sells for 32 dollars with upgrades up to v2.0. After a stable 1.0 is completed the price will be around 75 dollars for a commercial license.
The Current supported image formats that it opens and saves are:
.psd (currently working to support v8.0 and up)
.ani
.scx
.gif
.pat
.hdr
.iff
.exr
.ico.jpg
.jp2
.pcd
.bmp
.px
.ptx
.pbm
.pfm
.pgm
.png
.ppm
.ras
.tif
.tga
.wbm
.xbm
.xcr
.xpm
.xwd
.pcx
