There are many apps on play store/xda that helps implement spen on aosp ROMs (GMD spen control,note buddy,lg keyboard provides handwriting recognition,Asus gallery has air view)
I would really like to have a clean aosp experience on my n900
Note 3 N900 running VN-13.1 with stock kernel
Note 2 N7100 running phoenix ROM v17 with stock kernel
Nexus72012(grouper)running carbon ROM nightlies(full f2fs)with faux123 kernel .25u