I loved it. If you played (and liked) ico and sotc, then it's definitely worth it. The few complaints I've heard (usually revolving around the movement/controls) aren't really much of an issue if you played the previous 2.
At its heart, Last Guardian is an environmental puzzle game,more in the vain of something like Portal or qube. As in the previous 2 games, there's only minimal dialog and the story unfolds in a very show-not-tell kind of way.
And, for me, that's one of the things that really made this one stand out. It says so much without actually saying a word that you can't help but admire the world building and the way the story is told through the level design, architecture, and interaction between you, trico, and the world around you that it's one of those games where stopping just to check things out is a rewarding experience unto itself.
It's not that long, maybe 6-8 hours and well worth the time. The graphics, sound and everything else still hold up quite well and, for me, the gameplay loop of "enter an area, figure out the puzzle, move forward" is a good one.
So yeah, definitely worth checking out!