First half vs second half
Just watched it for the first time. My impression is that the film is composed of two, quite distinct, halves - the first half in a world of gangsters and second half in a world of hippies. I believe I'm not alone in saying that the first half felt far superior to the second half. Most of the interesting stuff, including the technical innovations, can be seen in the first half of the film. The second half just seems to go nowhere. Sure, it has Mick Jagger, who was the major attraction in the film at the time it came out. But watching it now it feels out of balance.
In that context it was interesting to learn from a documentary that the original script had planned more action and more characters for the hippie-part of the film. But for some reason, most of that was scrapped and we are left with just 4 people hanging around a house. It's a pity the script wasn't carried out as originally planned, it would have been interesting to have the full contrast of subcultures - the criminal and bohemian subcultures with all its different characters and activities. Still, it's a great film.
Here is the documentary about the film (in 3 parts)
https://www.youtube.com/watch?v=fikZwrIOpyQ