Comtypes is a good alternative I find to the win32 one which can be buggy, I have had great success controling Photoshop with maya's python interpreter this way. Actually if you look in my SIG at the psLink video that was all done with the openmaya api and comtypes with maya's built in python.
Quick note that I forgot to mention. The script will stop will stop and wait for the program to close. So, in the case of Photoshop, you would have to quit out of Photoshop in order to resume with the Python script in Maya (and possibly interacting in Maya too). Subprocess will also give you the exit code of the program (0…