What it comes down to, for me, is does Yellow Submarine look bad on blu-ray? No, it doesn't.
I know some purists want to trot out the same old arguments, but I'm sorry, I'm not joining them on this one.
If there was anything wrong with the PQ to me, trust me, I'd point it out. I'm sure some boring old tw@t will go through it with a fine toothed comb, looking for auto clean-up errors, ala South Park: The Movie. Power to them if they find anything, but not once did anything,(suspect live-action scene aside, which lasts what? Less than a minute, if that?) scream 'DNR!' to me.
Anyone that's even considering holding onto that wretched DVD, for anything more than sentiment purposes, or for the odd extra that wasn't ported across, is mentally insane.
Now, if you'll excuse me, I'm off to examine Warner's US release of Blade.