I mean lately I've been using it it has some good potential plays that you can use, increased movement speed when you flash, and boots of lucidity + distortion in total can knock up to 75seconds of your flash/tp/ghost. I don't ever see it being used, why is that?
I don't know. I always use them but often use mercurial with it
Flash and TP have a 3 minute CD each with Summoner's insight + Lucidities + Distortion
It's busted on champs like 
It's not really something you pick up until really late game or you have that 450 to so happenly spare.
really good on immobile mages like
Also good for some supports provided you take Insight
I think aside from the obviously powerful cases. (Such as Annie) Distortion simply works best when you are running multiple movement spells. Which you may only use on a hand full of cases. Top lane is a pretty good option for that with both flash and TP. But a lot of tankier top laners would pair that with Lucidity. (Rather taking swifties for the MS) While the Flash/ghost combo I've really only seen on TF. Going that rout means giving up a combat summoner, which could be important in a clutch case.
I run ghost on Hecarim so if I'm super far ahead I'll usually buy them for the AD boost when I use ghost
I like it when both of my summoner spells are effected, but if I've only got flash I prefer to just run faster.
