Think people are splitting into a few camps, but the general mood on here seems to be to go first for the King's Head on Essex Rd, with O'Neill's or the Old Queen's Head as back-up. The Litten Tree sounds like it will be pulling in quite a crowd too, but it's a shit pub and if that one doesn't work out i think you're a bit stuck for alternatives on Old Street. At least with the Essex rd you've got 3 options within a 5min walk of each other.
So here they are:
1. The King's Head, 59 Essex Rd
2. O'Neill's, 59 Upper St ( on adjoining roads)
3. Old Queen's Head, 44 Essex Rd
Angel tube is nearest for all of these (northern line), with Highbury & Islington (Victoria line) a little further out, or Essed Rd BR station.
For those of you who can't make it to Islington, the Famous 3 Kings sounds like it'll be pulling in a few west London reds.
I'll be heading for the King's Head on Essex Rd.
Enjoy it, wherever you are. feeling good about this one