Edit>Preferences>Customise keys - very similar to Photoshop.
Painter pro - the brushes emulate real media, therefore, if you are used to traditional painting then Painter is much more intuative than Photoshop. The brushes blow PS out of the water.
Painter con - the colour adjustment, transformations, filters and effects are inferior to PS. They are there, work and can be used but if you are used to PS then you will find yourself laughing in disbelief.
Now the overwhelmingly good news - both programs work wonderfully together if you save as a psd. I'm constantly flipping between the two and therefore I don't have Painter and Photoshop, I have a hybrid, dual program called "PhotoshopPainterCS311" 