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The PIL test can still be fixed before the final 0.9.0 release, it looks like we will need another RC anyway. Does anyone have time for this in the next few days?

I took a shot at fixing the ABI compatibility, and if PyArray_ArrFunc was the main issue, then that might be done.  An ABI compatible 1.6 with the datetime and half types should be doable, just some extensions might get confused if they encounter arrays made with the new data types.

Even if you fixed the ABI incompatibility (I don't know enough about the issue to confirm that), I'm not sure how much value there is in a release with as main new feature two dtypes that are not going to work well with scipy/other binaries compiled against 1.5.

I've recently gotten the faster ufunc NEP implementation finished except for generalized ufuncs, and most things work the same or faster with it. Below are some timings of 1.5.1 vs the new_iterator branch.  In particular, the overhead on small arrays hasn't gotten worse, but the output memory layout speeds up some operations by a lot.

Your new additions indeed look quite promising. I tried your new_iterator branch but ran into a segfault immediately on running the tests on OS X. I opened a ticket for it, to not mix it into this discussion about releases too much: http://projects.scipy.org/numpy/ticket/1724.

Before we decide on a 1.6 release I would suggest to do at least the following:
- review of ABI fixes by someone very familiar with the problem that occurred in 1.4.0 (David, Pauli, Charles?)

- test on Linux, OS X and Windows 32-bit and 64-bit. Also with an MSVC build on Windows, since that exposes more issues each release.