I just finished it a few weeks ago and enjoyed my time with it. The movement can be frustrating, as you would get the random jumping in the wrong direction, etc. Some people say it is your fault as the player and that it is very solid if you know how to play it, but I disagree. I slowed down on some of the "puzzle bits" and would still randomly end up in some strange direction. Some of it was due to camera placement (camera moves from free to a static shot for a specific part), but it wasn't just that.
That being said, I enjoyed it. I'd started it quite a few times, but played it through the Sequence 13: Bonfire of the Vanities, which apparently was DLC that is now wedged into the main game. I didn't have the patience for it, so I just watched a video of the ending.
Outside of those few issues, I enjoyed it and would recommend it.
GOG hasn't been Good Old Games since 2012. Yeah, they aren't really screaming it from the mountains, but they rebranded to just GOG.com then: https://web.archive.org/web/20120329190108/https://www.gog.com/news/bigger_fresher_newer_see_whats_new_on_gogcom