They believe it came from archean rather than bacterial sources. (Not really related, but many of our genes, and indeed one of our critical organelles, are also archea-derived, ie. the mitochondria.)
The genomic payload is large and comes with replication machinery (it might be a useful tool!)
Plasmids hold a much smaller payload than these units, and they're difficult to work with. Borgs are huge. If we can turn them into transfection toolkits, we can do larger scale genomic experiments much faster. That's extremely exciting.
Much of biochemistry research and understanding is done in bacteria. They're extremely useful little computers. We just discovered an extremely useful way to hack them.
In the wild, the gene payload codes for novel methane metabolic pathways. This also is of great interest. Not only for applicability to climate science, but also the natural ability to swap out or augment bacterial metabolism. Imagine all of the novel things you might swap in instead.
Who knows. These might wind up in eukaryotic cells too!