The type of people that gravitate towards the Nexus line aren't shy of a little ROM flashing, and they're invariably looking for that extra edge when it comes to performance. To that end, one of if not the first custom ROM for the Galaxy Nexus features a bevvy of tweaks and improvements to the stock ROM, the most notable of which is an EXT4-formatted partition, making for faster memory and storage access throughout Ice Cream Sandwich.
Other improvements in "Android Revolution HD" include a pre-rooted environment with the SuperUser app (naturally), removal of "bloatware", de-odexed for theme support, and various other speed and data hacks. Externally it looks just like stock Ice Cream Sandwich, including the new launcher and all the little points of polish that you're dying to get your hands on. Versions for the international HSPA+ model and Verizon's LTE model are available. Of course, you'll need a rooted Galaxy Nexus and access to ClockworkMod recovery to take advantage of any of this.
In what's sure to be the first of many, many Galaxy Nexus ROMs, an emphasis on speed is key. Roms from popular sources like Modaco and CyanogenMod are yet to be completed, but when they are, what do you want to see? Each ROM dev has their own special flair to ad, and others will likely mimic the addition of EXT4 and surely remove the US hardware's built-in Verizon apps. Leave suggestions in the comments section.
UPDATE: Whoops, looks like I jumped the gun - Paul "Modaco" O'Brien's Galaxy Nexus kernel supported EXT4 before this ROM. It's the basis of the modified Revolution HD ROM. There's also an updated version of the ROM over on RootzWiki, version 1.3.1.