Good Eviolite user
Has priority and boosting moves
Good coverage choices
It's in UU, which is not good when you're playing OU.
No recovery moves, which makes entry hazards a threat for it
Brilliant Special Attack and Speed
Nasty Plot boosts that Special Attack even higher
Access to things like Hypnosis and Focus Blast
Sort of frail
No reliable recovery outside of Rest
In UUBL, meaning it isn't quite OU-level
Hope I helped! I would prefer Gengar in most scenarios, but it depends on the situation, as Doublade is also quite good.