Looking through my emails-- I believe the original anthology was supposed to be 20 stories. Due to the Kickstarter, they were able to expand it to 24 stories. The first stretch goal was to include a story by Alvaro Zinos-Amaro; the second stretch goal was to add a story by Douglas Smith; etc. So that's nice they were able to get some names in. The Kickstarter had the additional benefit of donating "sponsored copies" to libraries, so there was a link for school and public libraries to request a sponsored copy. They were at 52% of their goal by the end of Day 3, so I was impressed they were able to get that much support for things. If I recall correctly, authors were paid prior to the Kickstarter launch.
Vanessa MacLellan, one of the authors, did a nice round of author interviews on her blog.
Visibility Fiction had a nice little write-up.
They sent out newspaper press releases. Since I live in the middle of nowhere, I don't know how that went-- I had the impression that it was part of a marketing package they'd purchased, but I'm not seeing the message that had given me that impression, so that may be an error on my part.
In addition to posting things to the internal FB group, the editors periodically send us encouraging words from parents/librarians/places that have enjoyed the anthology.
So-- I'm not really sure how the marketing side of thing compares to other "YA/Middle Grade Sci Fi Anthology Publishers" out there, especially since I'm not tuned into the publishing world like I used to be when I was in charge of YA/Children's at my library, and keeping on top of my publications/periodicals/what's-going-on-in-the-biz. I really do live under a rock these days.
But just judging from the amazing promptness with which the Kickstarter reached its goals, and then its stretch goals, they seemed to have a lot more visibility in the field than I had expected based on things like, say, cover design.
--edit-- If it helps any, my background was mostly in the unglamorous world of content-writing, so I was more used to writing my piece, sending it out, doing any edits, cashing my payment, and focusing on the next project, rather being super-invested and taking a super-active part in things to boost sales and royalties (like, say, I see a lot of romance authors do). So that's also part of my lack of being in-tune with that aspect of writing-- I just sort of figure publishers have marketing plans, and I pitch in where requested, but otherwise am pretty oblivious to how they maximize their own investment.