So if you take a look in the vscripts folder there's three scripts in a folder called surveys:

"end_puzzle"
{
   "id" 1
   "version" 2

   "onetoten"
   {
      "text"      "DIFFICULTY: Please rate the difficulty of this puzzle."
      "labelatone"   "Very Easy"
      "labelatten"   "Very Hard"
   }

   "onetoten"
   {
      "text"      "ENJOYMENT: Please rate your enjoyment of this puzzle."
      "labelatone"   "Very Little"
      "labelatten"   "Very Much"
   }

   "essay"   
   {
      "text"      "COMMENTS: Write any additional comments or observations you have about this puzzle [OPTIONAL]"
   }
}

And according to the VDC, theres a point entity called point_survey.

http://developer.valvesoftware.com/wiki ... 2_Entities

It appears this allows an in game survey at the end of the map.
So either:
Valve made this planning to have some rating service later on.
Valve made this but then decided not to use it.
Valve used it for in house testing/rating.

But it would be interesting to investigate this futher.

Edit:
There's no point_survey in hammer and I can't find it
in the portal2.fgd or halflife2.fgd and base.fgd

But typing 'ent_create point_survey' does not give me an error.

Edit 2:
So I created a point_survey in an empty map, loaded it up called 'ent_info point_survey'
There's an input called 'ShowSurvey', I call that and I get

(60.50) input : point_survey.ShowSurvey()
cl_show_portal_puzzle_survey: Error loading '.txt' from GAME\scripts\surveys directory

So there must be a keyvalue where you set the survey txt file, except I have no idea how to find out what the key is called

I'm willing to bet some money that this entity might be implemented when VALVe starts getting map distribution systems online.

I noticed references to the "survey" in some of the transition ents and the transition vscript file. It will be very interesting to see what comes of this.

Sorry for digging this out, but in case anyone is interested how the survey screens looks like:
end_puzzle_survey
test_survey
vista_generic

On the map sp_a3_portal_intro, for example, you can open it with the console command "ent_fire InstanceAuto47-transition_survey showsurvey". You could create surveys for custom maps as well, but I don't know if and where the results are stored.

This is more likely a left over from the beta testing. I know Blizzard used an in game UI for beta testers to give feedback on the WoW:Cataclysm content. I was lucky enough to get in on the Alpha/Beta and used it. This is probably something similar.