Level 20 Orc Hunter now. I have lost two fights so far. One to a +2 Druid (Murrdyn from Orb) and one to a rogue that got me from stealth.
So far I've beaten:
Mage - Even level to +4
Paladin - Never seen one so far
Shaman - Even level to +1
Other hunters - Even to +3
Rogues - Even to +1, but one kicked my ass
Priest - Never fought
Druid - Even to +2, but lost to one
Warrior - -1 to +4, pretty easy fights here
PVP in this game is really fun. I think I'll head to Ashenvale and try to pick off some Alliance tonight on Stormreaver.