Everyone should play a Death Knight, if only for two levels. Those two levels would take you through the introduction to the class, a bravura piece of showmanship, storytelling, and gratifying, villainous excess. It's unusual to find such a perfectly self-contained and satisfying single-session experience in an MMO. It enriches Warcraft's world and Wrath of the Lich King's main story immeasurably, and does so with humour and brevity. It's a perfectly encapsulated taste of what's to come.
It's also a showcase for one of this expansion's least-discussed but most profound changes: phasing. This technology finally allows players to feel like they're influencing events - or at least, feel like they're part of a changing world. What's remarkable is that it does so seamlessly, with minimal instancing or breaks in the experience. Complete a certain quest chain and a whole new encampment of quest-giving characters might appear for you, but be invisible to your friend who hasn't done the same chain - without removing either of you from the underlying persistent world for a second.
The system is not without its oddities, but it's a more integrated and classically MMO approach than, say, Lord of the Rings Online's well-crafted but rigid use of instancing for one-off story events. Story flows smoothly around what you choose to do, rather than forcing you along a set path, and only occasionally isolates you from other players. Villages burn, populations move, characters die, capital cities are attacked or overrun with refugees.
Phasing is used to spectacular effect in two gigantic set-pieces at the heart of Wrath of the Lich King's storyline - the Wrathgate quests in the first half, and the climactic battle for control of the Icecrown zone. These bring all the drama and spectacle of high-end raids to every single WOW player - and then some.
Until now, WOW's very best content has remained the preserve of the raiding elite. Wrath of the Lich King redistributes that wealth of experience to everyone. Every raid dungeon is now open to teams of ten as well as 25, giving a much larger proportion of players a chance of seeing everything in the game. Not just that, but some of the neatest tricks and challenges of raiding, the most sophisticated and rewarding bits of boss design, have been incorporated in the five-man dungeons - which are fewer in number than in The Burning Crusade, but of a higher overall standard (and this from the undisputed kings of dungeon design).
Even the solo player - which, let's face it, is most of us, much of the time - has had the same level of attention. In fact, you might say that day-to-day questing is the most radically improved part of the game. WOW's detractors have often pointed accusing fingers at its doggedly traditional monster-mashing quest design, and not without reason. Lich King is unavoidably built on the same foundations, and if you never again want to be collecting random animal parts for some bitch's brew - well, you're out of luck.
But the overall experience is a universe away. Burning Crusade improved the variety, density and reward of quests several times over. Lich King does it tenfold, adds more interesting enemy designs into the mix, and then weaves the quests together into eventful, entertaining, coherent and beautifully-paced pockets of adventure, studded with memorable characters and opportunities to break out of the grind, cut loose and have fun. One minute, you're using a mind-controlled abomination to pull ten enemies at once, and kill them in a single explosion; half an hour later, you're manning a cannon, shelling an angry giant from the deck of a pirate ghost ship.
Grinding isn't supposed to be this much fun. Where's the masochistic slog that MMO fans - gaming's hair-shirted, hard-working puritans - so love to hate? Consigned to the bin where it belongs, and replaced with a lavish, Catholic banquet of entertainment. Halfway to 80 - if that - and you'll already be looking forward to bringing another character through Northrend to do some of what you missed.