Like:
- it's Portal with alot more gadgets and puzzles
- more awesome story and dialogue
Don't like:
- huge rooms, even the simplest puzzles get rooms so big you haveto sniper shoot portals across the room to get things done, not to mention the tedious walking back and forth
- lack of complexity, mostly I take a long time to figure the puzzle out because of the huge room, so I haveto eyeball it or walk yet more to see it there is something across the room that I may need to get/hit, mixing the puzzle solving fun with part finding tedium... not cool
And minor annoyances with the feel of it(doesn't feel as smooth), but it's still a great game, I was just expecting Valve to polish out these things, but I guess they needed some extra time on those hats.