This game came so very close to actually being good. As has been noted in many reviews, the repetitive nature of the game is definitely a flaw, although if you're good at finding the shortcuts, hauling back the keystones from the altars isn't too bad.
What really breaks the game for me, though, is the enemies. Some of them aren't too bad, just occasionally pestering you, but the damned lynxes and buzzards are nightmares. They're absurdly aggressive, and do pretty substantial amounts of damage, and very much get in your way when you're trying to get around or solve puzzles. I got six keystones back to the central area before I just couldn't take it anymore. I just wasn't having fun.
The sad thing is, this could easily be solved by just taking out the enemies. Honestly, you wouldn't even have to take them out completely. Just make an easy mode with no enemies (and perhaps reduced damage from thorns) so people can actually enjoy the game instead of tearing out their hair in frustration over the unrelenting onslaught from the enemies.
Like I said, the game is almost good. If the repetitiveness doesn't bother you too much and you can deal with the incredibly obnoxious enemies, I'd honestly recommend the game very highly. It's got good visual and sound design, the gameplay is solid, and there's some good, fun exploration and puzzle solving to be had. I just can't stomach the downsides enough to keep playing.