@jreback, @cpcloud or others - can't do this check any more here, because of the change in how copying works (and because more ops end up returning views rather than the same object), I think identical is okay, because it seems relatively fast. I didn't see much of a change on perf tests, but they are relatively unreliable on my computer. What do you think?  I wasn't sure whether what mattered was whether it was the same object or if it was just the length...