To be fair, there's a lot going on right now. So, even if the installer was perfect, the actual packages (systemd, wayland, NetworkManager...) would be very unstable.
That's why Debian doesn't even place new systemd and wayland packages in the Sid unstable repositories.
I really don't get it - yeah, Fedora 18 was hard and I'm still looking for that missing half year of my life ;-) - but Fedora 19 release cycle was pretty smooth. One week delay is not bad in software industry . For Fedora 20 Alpha - we discovered one last minute bug and it would be pretty hard to release - wait for final fix and due to nature of fix, we would have to go through the most installer test cases. It would be doable but safer was to wait for well tested fix, that does not break anything else . On the other hand, this bug should not happen and should not be discovered so late but that's life of software developers!
Btw. Fedora 20 artwork is already done and I have to say, I like it ;-).