[Completely spoiler free]
Overall: If you like vampires/zombies, give it a shot. If you've some time to kill and you're not a serious stickler for writing quality, give it a shot. But if this is one of many series on a watch list, or you're not really sold on the premise, move on to something else first.
Specifically:
It's a great watch, but the writing definitely has its flaws. By this I don't mean that the plot is dumb, or obvious, or anything like that - it's actually really good when you abstract it a level or two - but the implementation of the plot is shockingly bad at times. Things are built up for over a season that end in 5 seconds. It doesn't help that it feels that some of the later scenes were thought up by the writers in a vacuum, who then tried their damn hardest to shoehorn those scenes in as they realised they were running out of time.
The characters are all great, but after a while some are almost annoying to watch, because it feels like we've seen their "time to shine" and already explored them fully, but they're still there for no reason other than to pad everything out. That said, it is nice that the majority of the main characters aren't just rotated out at the end of their arcs, as so many other apocalypse shows do.
The acting is great, the cast is great, the art is great (aside from the mandatory few CG quality drops that every show seems to have), and the locations are great. There's nothing else to say I guess.