Thought it was a good game when I played it years ago. Haven't played it since then though. I liked the concept, overall style, and the boss fights were some of the most unique I've faced. It's a really time-consuming game though, and not in the good way. There's a lot of wandering, riding, finally finding the boss and then trying to climb the damn thing. Still unforgettable though, especially when *THAT* part happens, and I'll just assume everyone knows what that emotional part is.
I have to agree though, the only replay value it has is increasing your grip, health, and overall time spent getting through it again.
It seems to be a matter of taste, I enjoyed a lot riding the horse through that empty land, the graphics were pretty good back then, the landscapes were also a nice thing to look at and the occasional bird flying over me was a nice touch. I replayed it many times, but each time the ride to the boss took a little, as I liked to wander around and explore that place. And the colossi, I loved the fights, and I don't usually say I "love" anything, having to climb them and search for their weaksposts made me feel so small, it was an awesome feeling.
I can appreciate the atmosphere when going to find the boss, don't get me wrong. I do anticipate getting to the point after a while though, though it's like you said, preference. Exploration can be fun in small doses for me. And they did do a great job in making you feel especially small compared to these bosses, especially during the last fight, which though long and tedious at times, I did enjoy.
You need a good sense of humor and a dark room for ambience. 8/10 for the experience itself. It loses points for not really having any replay value though I have done multiple play-throughs myself because I really like the story as a whole. Haven't played Ico yet but I believe it's tied to SoC in some way (I'll probably pick up the HD collection sometime later).