I've sunk over a dozen hours into it so far. It's a really enjoyable game, however it is truly in early access stage and the developer has made no illusions about that. It's playable, and largely bug free, but there's not a lot of depth available since many of the features are still in progress. Up to the release of the game, it's been developed by 1 person and he's hiring some additional staff but that all takes time to see fruition.
The graphics are beautiful, and the game has a great atmosphere. I love watching the buildings being constructed. The mechanics in the game work well, but there's a lot of buildings, resources, and advanced stages that need tweaking/implementing.
If you like what you see in the videos, and are OK with an actual early access game, knowing that features and improvements will be coming slowly, then id suggest getting it now. Otherwise, wait for the official release.