1) You cannot install 10.1 Roms (at least I couldn't).
2) You can easily root the 8.9 using the 10.1 patch file method. Upload the one that's posted on here in another thread to the device, reboot in recovery mode, install the patch, reboot, and it's rooted.
3) Last night someone posted a way to get Netflix working on the 8.9, which wasn't working up until then. The instructions for this are also posted in this forum.
Yes I agree that there doesn't seem to be too much activity or forums/threads on specifically the 8.9 model, but it's brand new and will become more popular over time. I was a bit upset without finding a way to root or get Netflix working, but now that I have, I am in love with this little device. It does everything I want to do.
Also, on a side note, if you want OpenVPN support, it has the tun module integrated directly into the kernel (unlike the 10.1 apparently), so it's easy to get it working if you're rooted. And Samsung just released the kernel source so there should be custom roms and kernels coming soon.