Lotro has the best playability I have ever seen in a game.
What I like most about Lotro is the fact that most quests are solo, with optional fellowship. You chose this when taking the quest. The dialogues in Lotro are also incredible well written. It's not only "Kill 10 boars because I need food for my family" kind of dialogues. And the main storyline is incredible capturing, sucking you right into the story and you feel like actually helping the fellowship of the ring.
Crafting in Lotro is very advanced and you can craft some incredible powerful items. Gathering resources is also done in a good way.
Probably one of the nicest thing about Lotro is the deed system which makes it possible to customize your character with different traits. It might take some time to finish a trait up to level 10 (which is the current maximum), but then again it's quite rewarding when you do.
Another unique feature I love about Lotro is the legendary weapons. Basically it means that you can level up your weapons as well as your character. And on top of that you have different legacies for the weapons and items which can make your items truly powerful.
All in all, Lotro is probably the most enjoyable game I have ever played and rivaling classics like Baldur's Gate and Fallout.
I can recommend this game from the bottom of my heart and now that it's free to play everyone can try it out and see if they like it.