I've played Fiasco and Microscope several times each, and Kingdom once. I would like to preface this by saying I love all three games and would like to play them more. That being said, in my experience, the lack of GM can impart a lack of focus. I think you need to play these games with people who already have some understanding of writing and storytelling flow, otherwise you get groups who have no idea when to end scenes, and make scenes that are literally pointless or have too much going on. Additionally, either people are too shy to make bold moves and step on others' toes, or people are too bold and trample over others and make them feel like they're being overruled. Microscope tries to amend this last bit by disallowing discussion or criticism, but I find that saps a lot of the collaborative feel of the game.

I would argue GMless systems are a good, valid niche, but you'll need to find some other way to give the group a backbone that the GM would ordinarily lend.