I've played through your map and it was great fun, the puzzles were challenging and inventive, like the last puzzle when you watch the ball on the monitor. I think a few things could be improved however.
Some rooms are very oddly shaped and can be confusing, so it's not always clear if you should be able to do certain things. A lot of the diagonal walls and surface for example don't fit in with the rest of the map (levels in the original game were designed to be movable and deconstruct/construct-able by Glados so nearly everything was square) Even though it's set inside a dream, It would make it clearer to the player what they needs to do.
Some textures are the portal surface, but you can't make a portal on them,(the ceiling of the first room for example I thought I would be able to put a portal there) Not a big problem though.
Some parts like the floor falling at the start which worked for me the first time but not the second time, the spinning room and the door opening near the end seem to break sometimes, or get stuck. You could try fixing the objects in the spinning room to the floor (Would be cool to see them upside down on the ceiling) You could try making the door at the end go up instead?
It would be great to see you expand on what you have so far, with a few more puzzles and some more explanation about the dream and what was going on, It would be interesting to wake up at the end of the map as Chell in the first room of the game, or have more puzzles with stuff upside down or completely different from normal.
Looking forward to what you do next.