Well, my collaborator has taken against a new plugin in the middle of building a large and complex model, and doesn't like the way it prefixes cross referenced component names with XRC- and layers with XR-. It means that components and layers that come from Cross References appear out of sequence with native layers in the main model
I think that is a small price to pay for the convenience it offers. And if, as recommended, you start with a completely empty main model, and Cross Reference in all the major sub-models, that problem also disappears if you use it from the start.
But I think it's great, and intend to use it myself to keep track of sub components edited separately in sub model files, even when working solo.
It is cleverer than the existing Xref Manager plugin, which I have also used, in that it avoids duplicating definitions of subcomponents that may already appear in others' sub models you have imported. And it has a more elegant interface
I had a little difficulty getting started with it, as it puts its main menu entry on the Windows menu and I took some time to find it. It doesn't go on Tools, or Extensions, where I first looked for it, which is unusual but not unprecedented.
I was also having problems initially in a very large model, which completely went away after restarting SU. Even though it was my problem, the authors were quick and helpful to respond to my tribulations.
Haven't used it long enough myself to vouch for its stability, but it has been in production use in the developer's own architectural practice for some time, without reported problems, and (he says) has saved his practice much money by avoiding having to migrate to much more expensive software for team development.
So is Layers Organizer from the same source. It's a significant development from the former Layers Panel plugin (I think that was the one), whose author had to abandon further development.