Maggie is a solid addition to any Horse deck, and she actually does great work in Gadget Horse decks as well. You can use her to fetch a Yagn's Mechanical Skeleton or a good ol' Mechanical Horse from your discard pile, using a Mad Scientist to invent it and then attach it to any dude in any location. Now that's synergy!

Here's the rules clarification on that combo being possible: forums.pineboxentertainment.com