I really didn't like it during the first 20 minutes.
I thought "here's Pixar showing how advanced their technique is".
Then it grew on me and I thought it was cute.
Not great, nowhere near as good as Mamma Mia, but nicely done and quite clever.
I liked it more when the humans came in.

Funnily enough I'd been tipped that the 5 minute short Presto before it was utterly brilliant but I didn't like it at all.
Far too clever for its own animated good.
I'm only a fan of animation when the script, plot and characterisation live up to the technique.

Delighted to say my brother felt exactly the same as I did and actually went to sleep in it!

I`m with your brother on that. I often fail to stay awake in the cinema. It`s a strange comfort or not comfort zone.
When you watch a film at home, there is a pause button for a tea break, sometimes I watch a film over a whole day with breaks.
In a cinema, you have to watch one segment only in bulk.
Also, I think had I watched the final Bourne film in the pictures, I probably would have felt quite sick at the editing speeds.
I hate a large screen when they suddenly expose you to a cliff edge or something similar.