Is there a need for the boolean type at all, other than backwards compatibility?

Currently, Arduino's boolean type is defined as an alias to bool (thanks, Chris--A!). However I don't see the need to have a custom boolean type when C and C++ already provide one.
Advantages of the bool type are:

• it is shorter
• it is standard
• it is consistent with other "abbreviated" C and C++ types such as int and char

I think it would be a good idea to stop using this custom boolean type and instead use the bool one; in my opinion, the fewer unneeded additions Arduino makes to the language, the better.
The steps for moving would be (in this order):

• Replace all boolean from Arduino core and library functions with bool.
• Update the documentation, removing all references to boolean and replacing them with bool (and maybe adding a note that the boolean type is deprecated).
• State that the boolean type is deprecated. An __attribute__ ((deprecated ("use bool instead"))) on the boolean definition could be a good idea.
• Eventually, a few versions after deprecating boolean, consider its removal. (Or leave it there forever, just in case.)