It is based on the 4.2.1 AOSP code base, where CyanogenMod will deliver a stock Android look alongside a host of customizations in order to separate it from the standard issue Android experience. Among the devices that support the new CyanogenMod 10.1 nightlies include the GSM Galaxy Nexus, Sprint Galaxy Nexus, Verizon Galaxy Nexus, Nexus 4, Nexus 7 (Wifi), Nexus 7 (HSPA+), Nexus 10, Transformer Infinity TF700, Galaxy Tab 2 7.0, Galaxy Tab 2 10.1, Galaxy S (some models), Galaxy S II (some models), and Galaxy S III (some models).
We are quite sure that this list of models is not going to just stop there, and ought to grow soon.