Movie watching (I've been holding off on watching Dune for this!), general-purpose computer-y stuff (browsing, writing, media consumption, etc), game streaming, using it as a larger display for a MBP, seeing what people build, and (maybe) building some things myself.

In general, I want to treat it like an iPad / MBP hybrid with enormous virtual screens that I can take around with me. There's a lot of potential for what could be built (especially with the AR stuff you mention), but having access to the majority of the iPad ecosystem, MBP mirroring, and other miscellaneous features already makes it an enticing device to me.