The mindcrack gang, whose server is in recent versions, just found that the couple of maps in item frames they had in the spawn chunks (which happened to show spawn, but I'm not sure if that's relevant) were causing significant lag.
I know our spawn is pretty laggy on LVS, I'm sure there's lots of reasons for that including just "there's lots of stuff" which fair enough, but maybe this could help? (We do have maps there... right?)