Expect more of everything you loved about the original - and vice-versa - in this content-packed expansion.
Most gamers will be able to make a decision on whether they are interested in picking up an expansion based on that first paragraph: Wrath of the Lich King is more of the same. Explorers have a new continent located at the top of the world map called Northrend, with most of its regions reflecting that title accurately. The vast majority of the map is filled with tundra, icy mountains, icecaps, and other respectfully chilly areas, with the exception of single lush jungle zone somehow preserved through magic or technology.
Death Knights, the newest playable class, are similar to the Forsaken in that they broke free of the will of the Lich King, and now they want revenge. The class is available to every race from Gnome to Tauren, and is designed to be able to perform the function of tanking of damage dealer (the third role being healing). Death Knights require that the player already have a character of at least level 55, as Death Knights start at level 55 in their own starting zone to the east of the Eastern Plaguelands. Through a series of quests, the player will go from employee of the Lich King to vengeful faction member in what is arguably one of the best starting experiences in the game. Even gamers not interested in playing the class are likely to enjoy the experience of the starting zone for the lore associated with the class alone.
Profession junkies will be happy to find hundreds of new craftable items as well as a new profession called "Inscription," which relies on magical symbols to enhance class abilities, as well as create magic cards and books. Existing professions have the additional items you might expect from an expansion to a new profession skill cap of 450 (up from 375 in The Burning Crusade).
Two additional battlegrounds have been introduced as well as new Arenas for games that enjoy Player-versus-Player content and rewards. The biggest addition, however, is the battle for Wintergrasp, a world PvP zone whose objective to an assault-style attack on a castle keep by the faction that is not already in control. The battle occurs every 2 hours and 30 minutes, and the controlling faction gains access to special vendors, items, and a dedicated instance.
The graphics also enjoy a significant boost in Northrend. Environment and mob models have been significantly upgraded, with vast forests caught aflame and detailed enemies and armor textures. Certain zones are "phases," meaning their content changes depending on where your character is in any given quest chain. Player models remain unchanged, as does most of the legacy items and extras from the core game, such as faction mounts and the original battlegrounds.
However, all the additional content is really just that: more stuff to do. Tank classes tank, damage dealing classes blow stuff up, and healers heal. Grouping continues to get easier with an improved Looking-For-Group tool, but the inherent problems of a surplus of damage-dealers and scarcity of healers can still make getting a pick-up-group (PUG) together tough. Items continue to scale, so as you max-out your character the "next level" becomes an exercise in dungeon-running to gear up for the most difficult instances and raid content.
Expect to be sucked into an all-new continent filled with activity - and bid adieu to your real-life - if you loved the original.