Got my mono set. It is seriously worth it. The packaging is just awesome, and the sound really is amazing. I'm hearing stuff I never heard before! Pscan's post on Sgt. Pepper NAILED it.
Tom, I don't think they gave a definitive number on the second pressing. I'd just advise signing up on Amazon to be alerted for when they restock.
I've been really impressed with how HEAVY some tracks sound. I was actually in shock when the guitar and drums first kicked in during "Paperback Writer", it rocked so hard. It really shows how piss-poor the 1987 remasters were in the first place. Oh, well. We were young then, I guess.
But yeah, the mono box has a thousand "Oh shit!" moments like that one, just waiting to be (re-)discovered: The first orchestral swell in "Glass Onion"! The for-some-reason-completely-excised-on-the-1987-CD first chord of "Yellow Submarine"! The bass on "What Goes On"! The more audible drums on "I'm So Tired"! It all sounds awesome and is a joy to listen to.
And for the record: Ringo Starr and Paul McCartney = best rhythm section ever. Ringo especially gets his due with these remasters.