[SP] Double Gubble
This map is ok. I don't like the lighting/atmosphere, but the puzzle is good. I like this confusing world portal. But it would be nice if there is an explanation room infront of the puzzle that shows the user how the think with
Very true. I remember a lengthy discussion back in the Portal 1 days, whether or not it's ok to use glitches like this, especially the one that KennKong describes a few posts back. (It was called "portal peeking" or "tunneling".) Many people hated it (mostly mappers, because it creates lots of opportunities to 'cheat' that are incedibly hard to prevent), but many other people would say that anything allowed by the game is a valid move. Some maps even required its use, including one with exactly the same setup you used here!
Personally, although I would never use something like this in my own maps, I did enjoy playing this one. Let's hope there won't be a change in the game code that breaks this glitch, since it really seems to be an edge case!
(Oh also, I know you don't care much for visual design, but in your future maps, please make the fizzlers only 1 unit thick. The ones that don't reach all the way from the floor to the ceiling look really weird.)
Other Portal 2 maps: Medusa Glare
Portal 1 maps: Try Anything Twice | Manic Mechanic
Heh, to be honest I'm not that bothered if it gets patched - like those old peekaportal maps, or the Portal 2 ones that relied on portal bumps for a speed boost. It's something you have to accept operating in this gray area I guess 
I don't think it's really in the same league as those other glitches though considering how rare it is to find the right setup, using this technique to the floor kills the player, and even when it is possible it's probably not that useful. I'll certainly have a wee look for the other map though; I like this kinda thing. Cheers!
Oh, just for you then