I suspect the need to preserve the C ABI would make a complete backport a challenge. I'm still tempted though, mainly to give third parties a robust core implementation of the buffer API to test against.

This is especially so with Python 2.7 still having a couple of years of full maintenance left - that's a long time to leave it with a known broken memoryview implementation. I'm less worried about 3.2, since the upgrade path to 3.3 is easier in that case, but even that version is likely to see widespread use for a long time.