First being in love with Dragon Age: Origins, or at least the world it is set in, I knew I would eventually pickup the Leliana's Song DLC. Like many people who played the game, you find that she is one of the more attractive cast mates, and not in a physical way, but more so in that she definitely has a dark past that she is hiding from, and one that the game itself doesn't really go into. The DLC is specifically for that.
If you've played the game, then you know one thing going in, and that's that she's been set up. You also know Marjolaine, her former teacher, and the DLC picks up on the night everything went down. The DLC doesn't stray into Orlains though, it keeps the content directly in Denerim, literally outside the Arl's Estate, so it's all familiar territory to anyone if you've beaten the game. This also keeps the size of the download to a minimun. Though it adds no real place that you haven't been it does repurpose those environments in a way that keeps it consistent, and kinda creepy if you have her in your party when you come through in the main game.
Like Awakenings and the Darkspawn Chronicles, this DLC brings in new characters that will only be seen here. The biggest difference with this one though is that for all the content, expect to only have a group size of 3. Surprisingly, this make a huge difference in the middle, where having that fourth member would have changed some of the fights, and actually makes you have to pay attention. I was used to running with 2 mages most of the time, so heals/damage weren't a big deal, and this DLC forces you into a mage/tank/rogue group. Be prepared to manage your heals, as there also is a limit to the amount you can actually pick up.
Most of the content is between about level 10-14. This makes it challenging, but not a breeze. Toward the end of the game, if you're used to the main game, you should be back in swing and killing like regular. Leliana is the same rogue you play for the most part, so if you had her in your party you know how to use her. The tank and mage are pretty open though, so you can set them up relatively as you need. Don't expect a ton of weapon choices though.
The DLC offers 100 achievement points as well. Also upon completion of a 50 point achievement you get an armor piece really built for Leliana in the main game. I didn't realize the DLC rewards were moving to the main game (except like Ostragar and Soldiers Peak, which are main game add-on's), so that makes completing them all the more reward for that second and third palythrough for all the badges.
At 560 MS points, it's a good investment if you want the achievements and liked the story. If you didn't care for the game though, there's nothing added on that will make you.