Idea!!
I have this idea, which I could not be set into action by me nor do I know if its posable but listen up.
If someone could make a map where it would consist of platforms leading up and up and up where you had to use portals to jump up to the next one and so on. The catch here is that you would be timed, that way there would be some sort of competion.
What do yall think, I would love to play on a map like that. I just don't think I would be able to make one like that.
If yall are confused, since I am a poor explainer then please ask questions.
Are you talking about a timed version of the series of platforms in the later chambers that you used conservation of vertical momentum to beat? Where you jumped down into a pit and then used that to propel you up and shot portals onto higher platforms while in the air?
And would the interesting part just be that this would be timed?
And would the interesting part just be that this would be timed?
Yup, except not only would it be timed, it would go really high and there would be a lot of platforms going up. You would go higher and higher and fall further and further and faster and faster. It would be even cooler if you could compete against someone and have two diffrent set of platforms one for each person, but I don't see that happening any time soon.
Justed wanted to throw my thought out there. 
Edit: I don't know how many people here have played Mario Party, but you know the Mini Games. Well one of the Multi Player Mini Games was a plant that grew all the way up to space and you had to compete against your friends to see who can jump to each leaf and reach the top the highest untill the time ran out. I though this would be cool using the portal gun and wanted to see someone make it.
In a multiplayer environment, I could see this being fun. However, seeing as how the game is single player, it would not be.
Only problem is when you reach terminal velocity you will then reach the same height every time you exit a portal, no matter how high you fall from.
There are two completely different limitations on how fast you can travel in Portal:
One is a literal Terminal Velocity, enforced by the general HL2 physics engine, which is the fastest that you can fall due to gravity.
The other is a portal transfer velocity limit, which is the maximum speed you will retain while going through a portal.
These two values are incredibly different! If you make a very tall, narrow room, and put a portal on the floor and ceiling, you will be able to tell that as you fall through the room you will pick up speed until you hit the portal, then lose a lot of speed the instant you go through the portal, and then pick up more speed as you fall through the room.