putting aside the grammar aspect, I think the ```x.none?``` is more useful.
say you have:
``` ruby
# check that all boxes are full
expect(boxes).to all( be_full )

# check that all boxes are not full
expect(boxes).to all( be_not_full ) # requires me to add method for - 'not_full?'

# so I would rather do
expect(boxes).to_not all( be_full)
```
in other usecases I may want to check ```!x.all?```
like @myronmarston said: ```that is, it'll pass if at least one of the items does not match```

but this can already be done by:
``` ruby
 # check that the boxes include at least a single full box
 expect(boxes).to include( be_full )

# check that the boxes doesn't include a full box
 expect(boxes).to_not include( be_full )
```

maybe we can add an alias to ```all``` which will make the negative form more readable... any suggestions?