I have yet to play against a good one. His range seems ridiculous at the moment though.
I actually like to engage without being in locust...
Also:
i dont think he is a too strong mid char but he might be quite valid in solotop if you got a good support/jungler/mapcontrol since he is gankable easy
I have yet to go negative with him. I can outlane almost any champ mid (brand is like everybody's hard counter :/) and I'm not afraid to get closer when necessary unlike most xeraths I see. I honestly saw one that got himself underleveled to level 6 when everybody else was level 11 or so because he was too afraid to get close and only used his locus of power and q.
He's going to be similar to many new champs recently, to name a few: Cass and Lee sin, oh, and urgot, Urgot is the epitome of this cycle
They seem balanced/slightly underpowered because they are slightly too complicated for people to master within a week, but give a patch or two when people start mastering them, qq commences and they get nerfed
such is the cycle
quaaadddd