It's Android update day for Nexus devices, apparently. Hot on the heels of an Android 4.0.2 update for the Verizon Galaxy Nexus LTE and the 4.0.3 update for the GSM Nexus S, Google is rolling out Android 4.0.2 over-the-air to the GSM Galaxy Nexus. We're not entirely sure why this version of the Nexus isn't good enough to get the "base version" 4.0.3 version of Ice Cream Sandwich, but regardless multiple reports show that it's rolling out OTA in some regions as you read this.
Presumably the 8.7MB update, which only reports that it "contains important bug fixes," does the same work for the GSM Galaxy Nexus as it does for Verizon's version (excepting the LTE improvements, of course): improved mobile hotspot when used with VPN, Wi-Fi improvements, louder audio in Google Navigation, and a bit more.
As with its other updates, Google is rolling this one out slowly — UK and New York users on T-Mobile have reported seeing it so far. If you'd like to update manually, it's unfortunately not quite as easy right now as it is on the Nexus S, but this post on XDA-Developers and this one on Android Central should get you started.