ACWL, what version is the server? I noticed that furnaces are still bugged, but this was fixed in an update; The server does not auto-update, you will have to re-download the file.
EDIT: here's a list of currently known bugs that you should be wary of:
Everything is invincible.
Mob spawners always spawn monsters, regardless of what the server says.
Placed fluids will not spread, and will disappear over time. (however, /giving yourself water or lava avoid this)
Grown trees are sometimes glitchy, leafless, or even invisible. (rejoin the server to fix)
Doors can split in half, or not let players pass even when open.
Pressure plates and buttons don't open doors.
Tools can be healed by dropping them and picking them back up.
Boats are invisible to other players, and cannot be recovered.
Seeds may be invisible to others, and unclaimable to you.
Chests:can duplicate or destroy items if you move them around too quickly.
Minecarts and minecart tracks: cause severe client and server lag, to the point of crasing both. DO NOT USE!