I agree that each of us should use what is best for them. Any software that you already have purchased is what is known as a sunk cost, meaning that the money has already been spent so the cost of it is not longer a consideration. Those who own
PSP and are used to it, then that is fine. You can always try using
gimp if you can, but if you find yourself to be more productive with your current software, that is fine.
There are some problems with
gimp, one is the lack of nice brushes available for download, as
PSP and PS have. Another is the lack of the large number of filters that can be downloaded or purchased.
In the past I used a variety of other paining software that is mostly forgotten by most people today. The design of that software was limited by the capabilities of the hardware of that time. Features that I now rely on like layers, didn't exist at that time. That is one of the reasons that so little postwork was ever done back then.
I started with
gimp when I didn't need anything too fancy. Just somthing to handle simple untility graphics work.
Once I was ready to get started working on art again in late 2004, I found that
gimp had become comfortable. I have a copy of
PSP that I bought a while back as a clearance item, but it does not feel comfortable. I can work with it but and given time it could become comfortable, but it is limited to running on Windows; while
gimp runs on each OS that use most often.
I have heard complaints that
gimp can not handle tubes, well that is true that it can not read
PSP tubes and it does not have a function by that name. Instead,
gimp has the same functionality of tubes built in it brushes interface.
As Rayera mentioned scriptFU That is one of the places where
gimp leave the other program in the dust. I understand that PS now has scripting capability,
gimp had it first and still has it best. Instead of providing it own custom scripting language,
gimp uses standard programming languages for scripts. It uses Scheme (ScripFU), Perl, and Python. Learning Python for eithr
gimp or
Poser you already know what you need for the other program and for writing independent software that can be run though a standard python interpreter. You can intermix the used of the various languages by a standard function registery provided by
gimp. Write a filter or other script in say python and it can used functions written in Perl, C, or Scheme that have been registered by
gimp during startup or there after.