They originally mentioned having a playable beta by the end of 2012 around the time WarZ / Infestation: Survivor Stories came out. Early access started Dec 2013 a year later... so yeah, about a year behind.
Yeah, stability is key in my book... even though it's Early Access, there's been some really poor pushes from the experimental branch to "stable" that has made it unplayable.
I noticed several of the bigger streamers on Twitch getting really fed up with it in the last few months. It'd be great to know how the teams are split up because it feels like a lot of the features are thrown in and never really refined.