> For example, we only have "everything's an object" behavior
> for some math intrinsics and the interface for files is a bit
> strange, e.g., I expected 5.cos

This one's been discussed a lot before.

> ...or aFile.rename('toThisName'),

I think the way to look at this is to think "who" it is that does the 
renaming.  In the case of a file, it's effectively the filesystem that does 
(eg in UNIX, it involves changing the contents of a directory file).

I think it makes more sense to ask the class (ie, the thing that logically 
knows *about* files) to do it ... hence, I feel this case isn't surprising.