I've had the annual subscription for a few years - the more recent the model, the better it is (some of the very oldest content isn't so good) and the models themselves are mostly fine with the exception of the trees which vary a lot in quality.
I generally always re-wire the textures, even when they are shown as 'Corona' versions they sometimes have weird IOR values or extreme bump - but the models themselves are reasonable.
I would say the best thing about it is how large the library is, even if it does need a little tweak before you can use it - still miles better than starting something from scratch especially when populating a big scene.