I'm interested in discussion and addition of features that are relevant to the ways in which Arduino is different than Processing.  There are lots of these: the fact that we're uploading to external hardware, that there are circuits involved, that there's a serial monitor, etc, etc.  

In the particular details of text editing and window management (as shared by Processing), you're right that I'd rather defer to Processing.  That still leaves lots of room for changes and improvements.

Again, the best way to ensure this doesn't get lost is to open an issue for it.

If there are specific things missing / extra, you may want to open a Google Code issue for them: http://code.google.com/p/arduino/issues/list.  Some C++ keywords may not be added (i.e. if they're not things we want to cover in the Arduino reference).

P.S. issue for a serial base class is here: http://code.google.com/p/arduino/issues/detail?id=60

I think it makes sense to define base classes for things that have implementions in the core, like streams.  For other things, it's hard to know what a good API is without concrete use cases.