Leliana's Song was fantastic!
My favorite of the DA:O DLC so far, except maybe Awakening, but that was practically a whole game so it's not really fair to compare.
It was really fun to see pre-Chantry Leliana, light-hearted and a bit amoral, taking such delight in sowing some mayhem. But she has lines she won't cross, and treason is one of them, and I loved watching her personality evolve over just a couple of hours, becoming the person we came to know in Origins. I love getting character backstory, and this one works really well for me.
How much do I want to see the previous adventures of Leliana, Tug, and Sketch? So, so much. What a great set of companions. If anyone has good fic recommendations, lay them on me!
It was extremely distracting to have Adam Howden voicing Silas. Seriously, when we found him in the dungeon, my first reaction, stated out loud, was "What's Anders doing here?" I immediately gave him the Templar skills because the thought amused me greatly, without even knowing that this would be appropriate for the character's future.
The DLC only gives us that one brief interaction between them, but Leliana/Silas jumped out at me from it immediately. I'd take fic recommendations for that, too, although depending on what's out there, I may just have to write it myself...
Nice touch, when we're going through the Arl of Denerim's estate the first time, to overhear Vaughan abusing a servant. My reaction was immediate and powerful: I wanted Leliana to break down the door and give him a taste of the murderknife, right then and there. And I haven't even played through a City Elf game yet (just did the origin, once).