Good: Fun, fast spawns create much chaos, very little lag even though servers are crowded Bad: minor bugs
Because SoM has just been released, the servers have been very crowded. That actually is a big plus for playing now, as there's very little lag, and the Orc camps in Mirkwood have such a high respawn rate that it helps to have a few fellow adventurers around to keep you from being overwhelmed (which is easy if you don't keep on your toes).
I've played the Skirmish tutorials and tried a couple of different skirmishes, and both were lots of fun. Also, the fact that you have a soldier with you that you can customize and improve on over time, adds a whole new dimension to the game (Skirmishes are like a game within the game).
I've only run into a couple of bugs so far, but nothing unusual for a new expansion, nor are any of the problems game-breaking. This is not as big an expansion as Moria was, but the fact that it came free if you had any monthly subscription, means that there's no reason to complain.