(The landmark is only needed as a formality, initially for back- and forward two sided transitions)

In order to use the exit transition correctly with the exit transition instance, create a point_changelevel and name it @changelevel.
With your exit instance you will have to collaspe it. Select your exit transition instance and go to the instancing menu and click collaspe -> selection. Doing that will automatically name your instance entities. You could rename them back to normal i.e. removing the AutoInstance1- prefix but I don't think it entirely matters.
Now click the trigger from the collapsed instance and add a new output: OnStartTouch->@changelevel -> ChangeLevel -> mapnamehere. You can resize the trigger to however big you want it, so then the area the player will start the transition is bigger.

P.S. @Brainstone: Portal 2 uses a info_landmark_exit entity and a info_landmark_entry entity for transitions.

EDIT: In order to spawn in the correct place, the landmarks need to be in the same relative position in the new map.

Took me a while to get trigger_changelevel working correctly, but if you want an example I've attached 2 maps to this post.

Map1 & Map2

If you walk into the black text on the back wall of the room, you will be transported from map1 to map2, and then you can walk into the black texture in map2 to get back to map1.

There is also an example in those rooms of how to use Globals between maps. In map1 the button on the right turns the global 'on' and the button on the left turns the global 'off'. In map2 pressing the button will display if the global is 'on' or 'off', this shows how the global can be used between maps.

Not sure about loading screens between maps now, I while ago I did play around with making a 'mod' and packing all the maps into there and then you could include loading screens, but looking at the page I used learn that, looks like it might not be working now since the last DLC. Maybe you could try playing and see what you can come up with...

http://www.se51.net/2011/09/15/how-to-make-your-own-portal-2-mod

HTHs,

Rob

Fracture wrote:
i found that testing to see if this works in my personal map. It had mixed results. The trigger wont react if you have noclip turned on, so if you turn it off, it does work

Why would you even want to transition with noclip on?

ChickenMobile wrote:
Fracture wrote:

i found that testing to see if this works in my personal map. It had mixed results. The trigger wont react if you have noclip turned on, so if you turn it off, it does work

Why would you even want to transition with noclip on?

Fracture wrote:
@chicken, I was too lazy to walk all the way from the beginning of the map to the end of it... In retrspect i guess i could have easily put a new spawn point right next to the trigger instead

Indeed!