I enjoyed it on the whole. The acting was fantastic, you might as well have been watching the real Niki Lauda at times. I like how they painted their characters warts and all, not simply trying to portray them as 'I want to win!' and 'I want to be sensible!' I had a fear it would have been dumbed down as opposed to simplified for the screen but happily it was very much the latter.
I was a bit disappointed with the manner of direction at times though. There's a real mish-mash of narration, editing and camerawork and it just didn't feel as cohesive as it could have been: it went from fast-cut editing to very filmic sweeping shots that felt very glossy, then there'd be vintage text overlaid... I just wonder if it could have been done as more of a contemporary documentary, which would have made the spool-on segments feel less jarring and allowed more vintage footage and so on.
Some of the racing was a bit underwhelming too - Senna showed how exciting an extended cockpit camera shot is/was at the right moment. It almost went there a couple of times but didn't, which was a shame. I know the film wasn't about the racing per se but it was the same few 'from the grass by the apex' shots and forward-facing wheel-to-wheel over and over.
Still, I think making it at all is quite the achievement and it's a good film.