As of right now, there doesn't appear to be a fully usable ROM, just pretty much home launcher modifications, they still have the underlying Barnes and Noble junk. I think the big reason is the system partitioning done on the hardware makes it difficult. The most promising looking rom appears to be the CM9 one, as it looks like that cleaned (or merged) the partitions so that you won't have the annoying limitations on space. Essentially making it a Galaxy Tab 7.7.
That being said, it seems to me, that the fastest way to get ICS on it, once the partitions have been cracked would be to port it from the Motorola Droid Razr. Reason being is that both use such similar hardware it is hard to distinguish one from the other spec wise and I would imagine since they use nearly the same resolution as well, some minor tweaks would be all that was needed. (I am not a developer of course.)
The Razr runs a Ti OMAP 4430 dual core @ 1.2 Ghz with a PowerVR SGX540 GPU. The Nook Tablet runs a Ti OMAP 4430 dual core @ 1Ghz with POWERVR SGX540. They both have 1 GB of RAM, both have 16 GB storage. Essentially, the Nook Tablet is nothing more than a large Motorola Droid Razr.