I never utilized any of the other map sources that Valve has released for their past games, but I actually found it useful to open up 2Fort last night and look at it to see how Valve did some things.
That's the way that source files should be used - that or slightly alter the map to a different game mode, like someone took 2Fort and made a decent arena map out of it.
Then you got the people that shouldn't be looking into the source files, and wasting other places space and peoples bandwidths.
Like there's a huge contrast between the following two maps that utilized the sources.
Arena_2Fort
2Fort...time sunrise....
The second is a complete waste of space and should have been left on the users hard disc for his own personal amusement.