After upgrading from 1.7.9 to 1.8 on server (clients mostly 1.7.10), approximately 25% of chests (and content thereof) are missing. Does not seem to be any particular pattern - see left hand side of first attachment for gaps where chests used to be.

Additionally, a bug around a water feature - see second attachment.

World is Vanilla, never had any mods attached on server or client (except Optifine on the client on occasion). World was originally created in March 2011, so some terrain is old Beta type. To date, only issues have been found in 'old' territory. Have not looked everywhere yet though.