Bard - a must until deep into POP
Monk - a must because it's a free 40 attack power buff no matter what you have in your group/raid, and, most importantly, changes your fist damage to 23/26, which you can't replace without raid weapons.
SK - no, you can get better dps weapons, and it's a terrible tanking weapon
Paladin - no, same as SK, except its a better tanking weapon than the SK epic
Ranger - yes if you need slow procs, no otherwise you can get better items from the bazaar
Warrior - Yes if you can't get raid drops (boc/hategiver/etc)
Rogue - eh, the haste is nice for an offhand
Cleric - yes
Enchanter - nah, only good for tank buffing, or quick hasting if you just died
Mage epic - nah, at this point fire pets are retarded damage
wizard epic - no
beastlord - yes, unless you can get raid gear
druid - no
necro - no
shaman - no, but it's really easy to get