I could expand a lot on this, but here's the gist of what I think:
I give it about a 3 out of 5, and that's being a bit generous since I love Doublefine/Tim Schafer so much. The art is serviceable (despite a distinct lack of Scott C. contribution), the lack of voice acting is shocking (while I don't think it is required, DF has done very well with this in the past, and the game's aesthetic screams out for it), and the gameplay is both stale and needlessly complicated. Don't copy something (Mario RPG for the most part) and actually make it worse.
I really enjoy the aesthetics - it's exactly how I picture my childhood Halloweens, and how I hope ones in the future will be when I'm older. The environments are fun. Even the battlefield backgrounds look very nice. Enemies are pretty boring overall, but it "works" in the most benign way possible.
The game just has next to no polish, which is underwhelming (not necessarily disappointing). It just doesn't feel like Schafer was around at all, as it lacks his little touches, attention to detail, and the whole "every scrap of the game contributes to the whole product." It just feels halfhearted, in a way that screams out "Man, I wish DF made more money because I love those guys, and then they could in turn develop a game like this more and make it better."
In the end, I'd love to see a sequel that expands on the entire product. Build more adventure elements into the overworlds, simplify the combat while also adding in an item system, and fix some of the smaller technical issues (FPS dips, getting stuck on invisible walls).
Solid, but my expectations for a DF game tend to be skewed higher than most companies, and it just didn't feel like their hearts were in it.