My pvp server is listed as "medium", but the horde population outnumber us 3:1. On any given time of the day there isnt more than 30 90's in Stormwind.
I really hope they look faction balances when connecting, i think the "well, one we balance the factions, they will be unbalanced again soon" statement its just to save themselves time and troubles. I know that a lot of my friends on my server are waiting for this update, if they dont merge us, or merge us with a low pop alliance realm, a lot of them will unsub .. and ill probably do aswell.