I recently discovered that the SCXI-1600 is not supported in 64-bit Windows. From what NI has told me, it is possible for the hardware to be supported, but NI has chosen not to create a device driver for it.
I'm a bit perplexed by this position, since I have become accustomed to my NI hardware just working. It's not like NI to just abandon support for a piece of hardware like this -- especially one that is still for sale on their website.
Please vote if you have an SCXI-1600 and might want to use it in a 64-bit OS at some time in the future.