Every alliance has its horde, and though you can't create that pet Balrog you've always wanted, you can join the dark side in PvP battles. Visit a "Monster Controller" NPC, and take control of an orc, spider, uruk-hai or warg for a time, doing your part to make the world a nastier place. Fight goody-goodies unlucky enough to be in that part of the world, and earn "destiny points" that can be spent on temporary buffs to stats and experience when you're ready to join the righteous again.
The basic mechanics of play and socializing seem solid, but the most engaging aspect so far is the storytelling that draws you into the world. Larger-than-life characters like Elrond, Gandalf and Gimli make cameos early in the game depending on where you start, and different quests interleave in interesting ways that make playing multiple characters more rewarding. For example, an early elven quest sends you scurrying around Silver Deep, where you'll encounter a huge troll frozen in a stray shaft of sunlight. Start life anew as a dwarf, and you'll see firsthand how that troll came to meet its end. We can only hope that these moments of awe and wonder continue throughout the game, and that the disjointed bits - such as when you talk to an NPC and then, BAM! - you're suddenly 100 miles away and locked in battle - will be smoothed out as the beta phase moves toward completion.
Shadows of Angmar won't be out till the Spring, but we're already addicted. How can that not be a good sign?