Cool! I think i take issue with "fine motor control issues, but not much more", though. Fine motor control's a really important feature of human intelligence, don't you think? Do you think the cerebellum isn't as efficient as it could be or that the number of neurons dedicated to the task reflects how computationally intensive motor control is?
I suppose a possible investigation of that question would be, say, comparing our cerebellum to that of another animal with extremely good fine motor control, like the cephalopods.
Depends on what one means by intelligence. People with cerebellectomy have difficulty with balance, but it doesn't really interfere with their general intelligence or their sensory experience.
I think the cerebellum is no more or less efficient than other areas, and I don't know if "computationally intensive" is the right way to look at it. The cerebellum really is similar to GPUs. GPUs use a lot of silicon to do constrained, repetitive tasks efficiently, but they don't support general processing models outside their narrow domain.
It's hard to compare with cephalopods, though they're very interesting, because their neural architecture is so radically different from ours. For starters, ganglia in their arms allow each arm a certain measure of independent activity. E.g., arms that get severed can try to "feed" the mouth for up to an hour after detachment.
I suppose a possible investigation of that question would be, say, comparing our cerebellum to that of another animal with extremely good fine motor control, like the cephalopods.