Probably already been written about by anons far more eloquent than I but I figure I'll throw in my two cents.
Zenith is an absolute mess but it's a fucking fun mess. 
Servers not showing up half the time, voice chat not working through multiple restarts. Tons of places on the map you can fall straight through. Combat's pretty samey but abilities feel real nice. Quests range from 'kill 10 rats' to 'explore the environment to find a way to reach xyz and then climb around to your objective' which is more fun than I thought it would be. Gliding feels fucking amazing with the advanced setting turned on. Map is huge but I get the feeling later content is much less fleshed out graphically.
Overall it's extremely rough around the edges but I think there's definitely a solid base to work from. The core gameplay feels good and is mostly bug free, surprisingly. 
Would buy again.
Gliding is so fun, bros.