I use devices groups as a way of separating my different sites. I can click on syslog for example and can choose a particular IP i want to view. However, with 1000+ IPs this becomes unmanageable. Device groups solves that problem for the most part.
Ideally when searching the categories below, i could choose a device group. I could then choose all the IPs in that group or specify a single one. There might be more, these are just the ones i came across.