I just finished it. Pretty cool overall, with some funny conversations and situations. You could probably play through the whole thing in like 2-3 hours, but I took my time, and had some distractions as well.
There's one quest chain I missed until after I finished the rest, and I really wish I'd found it earlier so I could work on it while doing other quests. I'll try to be vague as to not spoil anything. You'll get a quest early on that takes you south about halfway across Hallows End. When you do that quest, go all the way south to find the ones I missed. I'd do the first couple, then go on about doing the other quests in the DLC.
More specifically (though still avoiding some spoilers):
[spoiler]When you do the quest called Pumpkinhead, go south to the southwest corner of the map and you'll get a series of brain collecting quests (sort of made obvious by the fact that brains are dropping from the zombies you headshot even before you get the quest). First 10, then 25, then 50, 100, and 250. The 50 and up ones will be a lot easier if you can do them as you complete other quests. There's an achievement on the 360 for doing them all, but you PC guys may not care.[/spoiler]