A smattering of new units, A whole new set of campaigns, brilliant new cinematics and a storyline to kill. The Frozen Throne is a true heir to Blizzards Reign of Chaos. The Campaigns include leading Elves as they rebel from the alliance, Commanding King Artha's forces as he lays siege to the remnants of Lorderan. Taking a Night Elf Warden as she chases down the Evil Demon-Hunter and something unique amognst the Warcraft games, a strong RPG based adventure based on the adventures of Rexxar and his Troll Friend Zul'jis.
The Upgades to Battlenet are extensive, like whole new Clan setups, AS new ladder, level comparison (No more versing level 20's) and an updated team play option.
The new units are well balanced and - in hindsight - obviously needed, these include new Elven Units for the Humans, New Spider Units for the Undead etc.. . Now you can hire Mercenary Heroes to lead your Mercenary Armies and a new hero for every race.
In conclusion, Frozen Throne is not the sort of expansion pack you'll play once, then sit back and regret for a long while (Cough, Cough EMPIRE EARTH cough, cough)