GSM version has 4.0.2 update, but not pushed over.
i have manually downloaded the stock image from google and manualy flash it.
i am now running 4.0.2
what i did was,
backup my system (just incase).
Factory Images "yakju" for Galaxy Nexus "maguro" (GSM/HSPA+)
(all file extract from the 4.0.2 (ICL53F) image)
and reboot, and presto. you are on 4.0.2.
my experience, this does not remove all your data.
just similar to a upgrade for me.
a side note. i am running everything stock..