Well, I finished it, and it's unpredictable to say the least. But it's great. I prefer it to Ico. Ico was much more subdued, and I think it relied on the emotional attachment to Yorda to get you engaged more than this relies on the player connecting with Trico. That was really the only trick Ico had, and it did it very well, but Yorda was definitely a burden at times. Which isn't necessarily bad, but personally I became protective of her in a possessive kind of way. Like I worked really hard to get her this far, you fucking shadows aren't going to fuck it up now. I'll hit you with my stick!
Whereas the boy and Trico are much more of a team. You both worked hard to get to the end, and it's satisfying (instead of relieving) when Trico works properly. That's partly the limitation of the technology with Ico, and I think now a remake could make that relationship so much better, but The Last Guardian trumps it.
And even so, if you don't get swept up in that bond between boy and beast, the game still a has huge, cool, action packed set pieces to carry you along. The first big one was shown in one the previews I think, on the wooden bridge, but that's only the first part of it. And there's a few others along the way. It's a bit like Uncharted in an odd way.