Unlike previous 5 man instance in Wrath of the Lich King, all the bosses in this instance drop epic item, the main difference between normal and heroic loot is the item's level: 200 for normal and 213 for Heroic.
The Heroic boss will also drop Champion's Seal, which can now be used to buy a lot more things than they could in the previous patch.
The Trial is fairly short instance, consisting of only 3 encounters.
The first encounter is a 2 part battle against the champions of the opposite factions. You will first face them in a jousting contest, much like the Argent Tournament daily quests. Upon defeating them this way, you will then have to face them in a more traditional way.
The last boss of the instance for both faction will be the The Black Knight.