It does not work on a Mac.
Regarding difficulty, that is a relative question. In general, no it is not difficult for the more basic, automatic features. Consider downloading it and reading through the tutorial. The evaluation period is 30days with no limitations.
PTGUI, PTAssembler and Hugin started as front ends to Panotools, all using the Enblend, Smartblend and Autopano plugins. All have continued to evolve. Intially I tried all, settling on PTA at a lower cost than PTGUI, but just a good, at least for the panos that I produce. I have not looked back for several years so I am not aware of the current state of PTGUI and Hugin.
Happy stitching. Tom