First, it's a very bright film, which I'm guessing had something to do with needing an adequate base for the CGI, or the fact it was filmed at 120fps.
Second, the first time you see a de-aged Will Smith's face on what is likely someone elses body(?), it's a bit freaky.
Thirdly, seeing his current self and his younger self on screen at the same time gives an appreciation of how far CGI has come over the last 20 years or so.
It's not a "great" film, but it is certainly pushing the technical boundaries of what is possible...
Incidentally, Lorne Balfe who did the music also did the same for the recent BBC adaptation of 'His Dark Materials'.