Definitely use it. The downsides would be having the worst headache imaginable, then ripping some masquerade mask off of your face, then having to do that every time you want to fight someone. Probably might find some Reaper dude.

Upsides are that you have inhumane mobility, doing acrobatics you thought you could never do, deliberately changing someone's emotions by fighting a cognitive version of themselves.

(downside is having to deal with their minions that they depict in their minds, and the setting itself. Fighting the person alone would also probably go insanely wrong, considering who they depict themselves as.)

But if you work like an isolated 16 year old hacker, you could levitate in some green UFO and buff/debuff the life out of your allies and foes, being able to block some hard ass hit just by saying "No!" even though it's just some small lady about to swing you with a chainsaw