It's attained semi mythic status partly due to reasons already pointed out earlier on this thread (no appearance on early compilations or on any original album) and partly as a trailblazer for the "Revolver" sound of jangling guitars and thunderous drums.
The thing which always struck me about it was how LOUD everything was... a richly textured, powerfully mixed track but the vocals are always top of my tick list on listening to any Beatles number, and they're somewhat swamped here by admittedly spectacular layers of terrific instrumentation - again, each Beatle firing on all of their respective cylinders, with overwhelming results.
For years I thought those lyrics ran "That when it rains and shines...it's just coz they don't mind..." and only ages later twigged that Lennon was referring to a "state of mind..."
"Can you heeeaaarrrr me?"
Not too clearly John, no - there's just too much else going on!
Interested to read drummer tkitna's lukewarm response... is this really Ringo's finest hour at the kit after all?