CM9 is pretty stable for me, but the performance isn't as good as CM7. I'm using eyeballer's non-opengl builds, which are (for me, anyway) a bit snappier and less buggy than the opengl version; see the relevant threads on XDA. However, I've been using it exclusively for a couple of months now and I'm not going back.
ICS itself is much nicer than GB, and I get to use "tablet" versions of apps, which helps tremendously.
I switched over from CM7 a couple of weeks ago and am using the latest nightly version of CM9 and it's been pretty stable for me so far. Some of the apps that work in CM7 don't work as well in CM9, but that's mainly some of the games. I did find that you could set up your USB connection using Nook Tweaks just like you could in CM7. I have downloaded and read library books using the Kindle app without any problems. DropBox also works fine. Live Wallpapers seem to have more problems in CM9 than CM7.
I'm using an 8g and 16g Sandisk class 4 cards with no problems. Here is a link to the source I am using:
"did find that you could set up your USB connection using Nook Tweaks just like you could in CM7."
Glad that issue has been resolved!
I had CM 9 on my NC and removed it in favor of CM7.
No hardware accelerated video. Until that is fixed it will stay on CM 7.
It's the same deal with the alpha build for the nook tablet. I will stay on my rooted, ota blocked, stock OS until they solve the GPU acceleration issues. After that it's game on.
To be honest I don't see either the NC or NT getting GPU acceleration. From what I understand the driver is closed sourced and no one has been able to reverse engineer it. I could be wrong, but look at this way. ICS has been out for a good while now. Other devices are running it just fine. So why is the NC not getting hardware acceleration in the UI and apps? CM7 and stock and MIUI and other ROM's can do it.
CM9 is pretty nice. I also notice that the non-opengl versions are much more stable for me. I kind of miss the video. Youtube works if you turn off hd. Netflix doesn't work yet. I like the tablet versions of stuff more than I like netfllix right now. If i was going on a trip i would probably restore my cm7 backup to watch videos on the plane though.
If you can live without video you'll probably find that the tablet versions of apps with CM9 provide a nicer experience.
How did you remove it and do you think the removal process would work on a Nook Tablet?