Look for the "Search\/" icon and have at it - you will get a LOT of opinions and also facts on PC installs, maps, benefits, and problems.
Strictly speaking, you don't need a PC. When I installed one, my goals were to lean the bike out a tad (especially considering that I live at 4300 feet altitude), and to sharpen up the throttle response. Job done - I got what I wanted. What I did not get, nor expect to get, was noticeably more power.