Ted Mills’s review published on Letterboxd :
Docked half a star because the inventiveness peters out in the end, and how the "battle of Pepperland" is just not as headtrippy as the previous 3/4 of the film. Still, when you read up on the making of the film--seen as a risky investment, very little budget, no time, and an animators strike half-way through production--it's stunning how timeless it all seems now.
On top of the Pushpin-style cel animation, we also get:
Pre-Gilliam cutout animation
Looped photo figures that both look backwards at Muybridge and forward to our love of animated gifs
Flicker film (a la 1966's Tony Conrad)
Abstract rotoscoping (in the Lucy sequence)
pre-Sesame Street Numbers animation
There's no way today such an important intellectual property as "The Beatles" would be taken on by a company flying by the seat of its pants and just bunging everything in, mostly without a plot. Yet, here it is, a masterpiece.
(Seen on its 50th anniversary tour on the big screen, so crisp that I could see the shadows of the cel animation on the background)