I've seen people either praise or condone his run based on what he says but really I can't tell until I actually read it. I'm not thrilled that he says he's going to keep the lighthearted tone because, well I wasn't thrilled with the Giffin/DeMatteis version of a fun Booster Gold book. I can't be overly worried because I've only read things he's written with Snyder. You can't really get a feel for a writer when their co-writing unless you already know their tone.
As for what he says well...
I'm annoyed with the usual emphase on Jason having anger issues. First of all he's not the worst tempered Robin, that award would go to Damian. Because Jason never got near to the crap Damian has done even if you believed he pushed that guy. Plus showing anger issues now that he's calmed down with Kori and Roy around? That sounds like a huge backstep from what Lobdell has done. Yeah there will likely be anger from DOTF lingering but we'll see where that goes.
I'm not sure if he got the same vibe from Lobdells' writing that I did. Sure Ducra was trying to teach Jason to better control his rage but even she admitted that wasn't the prime objective of her teaching. When he confesses the need for vengance she tells him that their time together wasn't about making him perfect. She knows he'll overcome his rage--in time--but his training was simply the first step. Killing in it's self wasn't a problem for the All Caste since they trained him to be an assassin. They believed in certain rules for taking a life that he doesn't embrace until he see them again.
Also, Jason wasn't trying to be a hero by killing, not in his own head. He doesn't think of himself as such. He's even said he's not one in this title. If heroes let people like the Joker murder innocent people why would he want to be called a hero? Oh lord not this "he has darkness inside of him." Look I know sometimes writers' thought don't transfer into their writing, like a lot of the things I hated about Winicks' opinion on Jason wasn't in his early writing. But no, I don't want to see any of this crap about the poor street kid always being the one with darkness inside of him. Jason was a good kid, even in Winicks' Red Hood origin stories Jason helped others even if it threatened to blow his cover, he wasn't prepared and even when he was a kid with a head injury that only followed his instincts.
This makes it sound like he's a jedi having to chose if he rejects the dark side of the force instead of realizing there are grey areas. Even Batman himself isn't a white knight, he's done some pretty objectionable thing in every canon. (Like OMAC, his plans against the JLA, etc.) Maybe not the same shades of grey as Jason and other anti-heroes but he's not perfect. Plus Kori and Roy both kill, are they having the same trouble? Since Kori was raised in a kill or be killed enviroment I doubt she'd see the sense in not putting an end to a threat. She's pretty much at peace with her past as of the space arc, at least as far as her sister and race is concerned.
I think Tynion has a lot of good ideas in this, at least it sounds like it, but he either sees the series differently or has worded it oddly. Hard to tell which. Like I said this has nothing to do with his writing of the series but these were just things that bugged me in his interview. Nothing to base the book by.
As for the one word spoiler, unless it's Hugo Strange I have no idea.