Watched it a couple of days ago, I have to say I thoroughly enjoyed it.
I was expecting "Inception" level mind-numbing thinking but instead it was utter confusion in the second half

No, that's not a bad thing once I did my own reading.
Once again, a Nolan film worth watching (and necessary if you want a better understanding) a second time.
No spoilers, but I knew the film was going to end in a way that will make you rethink from the start
Overall, this has to be the most 'Nolan-istic' film to date - - the music score is tantalizing with inverted tunes while the visual effects are an absolute splendor + the use of time devices.
My absolute favorite moment of the movie has to be when The Protagonist steps out for the first time and everything is inverted (and he attempts to drive a car). I could literally feel it haha... such a brilliant sequence.
The creative use of inversion in the second half during the battle really makes the film one-of-a-kind.
Didn't watch it on IMAX due to distance and showtime, but this film was made for IMAX.
Highly recommended if you enjoy mindf*** movies + Nolan's previous works especially "Memento" & "Inception".
In terms of filmic quality + how mindblown it is compared to "Inception", yes, "Inception" is better at that but this film really holds on it own.