My controller died in the middle of Titan Ex once because I wasn't paying attention to the battery. While dead, I quickly switched to keyboard/mouse mode thinking I'd be able to at least get the fight done--and hey, Titan never even hit me once after that! ...Because I walked myself off the edge within three seconds.
People who can play with keyboard/mouse seem completely strange to me. Any time I try, the movement feels so imprecise and all the different keys... Blech.
Though it has its issues (targetting on controller does pretty much suck, even with custom targetting settings), the ease of movement and the hotbar far outweigh the negatives in my opinion.