in the clip they showed, Margot sounded just like she did when she was in "Neighbours"! Now, given that Tonya has a very distinctive voice, it is going to be very surreal hearing "her" talk with an Aussie accent...
Trust me, there is nothing remotely Australian about the accent she uses in the film. She does use two variations on a regional US accent - one for the skating-era Tonya and one for the older, interview-era Tonya - but they are definitely regional US accents or at least a solid attempt at them.
I found the film fascinating, less for the skating aspect of it (interesting though that is in its own terms) than for its discussion of overt narratorial unreliability and use of fourth-wall breakage to underscore its own inability/refusal to present, or even aspire to asserting, some form of truth. It's in blatant defiance of the film medium's assumption of verisimilitude, and it was really effective. The scene that sticks in my mind most of all is the one shortly before (IIRC?) the Olympics skate, with Tonya in front of a mirror with her makeup half-on and so garishly stark under the mirror lights that it looked clownish, smiling to the point of grimacing and all but breaking down. It was brutal, and very well done. The whole film also has a lot to say about the intersections of poverty, class, education/lack thereof, gender, ambition, fame and money in the US, and it's not so much asserting any of them as a truth about Tonya Harding or figure skating as a whole as it is using one very well-known story that happens to include both as a hook to hang the analysis on.
I wasn't sure what I was expecting from Alison Janney's performance based on reviews etc, but I thought she gave a phenomenally restrained performance - there are moments where all of LaVona's monstrosity, and also all of her humanity, come through in her utter lack of emotional reaction to things you expect to see a reaction to and the hints as to why that lack of reaction is there. There's one crucial scene where not only the audience but Tonya can tell that something isn't what it seems purely because that lack of emotional reaction isn't present. It's played that LaVona's emotional reaction is the one thing Tonya has ever really wanted and needed in her life, it comes at the one moment when she most needs it, and it's the biggest betrayal of all. Really great storytelling both in the script and in the performance.
In a weird way, though, I also found the film very Australian and could see what got Margot Robbie attracted to it and involved in it. We have a huge history of criminal-as-ambiguous-antihero narratives here, going right the way from the Kelly Gang and Ben Hall all the way up to Chopper and the various Underbelly miniseries, and with the exception of it focusing on a woman and refusing to either glorify or minimise violence, either that experienced or that committed, I, Tonya very much fits in the trend!