So, I was going through my library...

...and I found that, after all this time, the UDK on Steam is still just a text file. Even though Steam software now exists and would be actually really handy so I didn't have to keep downloading 1.6GB "updates" everytime there's a new beta version of the UDK out.

The best bit is that if you launch the test game, the UDK has Steam achievements which you can unlock, but nobody can ever see them...