It'll do Johnston good to head to a team that has a very specific role and need for what he offers. He also moves well enough and can play at a certain modicum such that he's not simply a liability when on the ice. Perhaps he can even do more in an expanded role?
Everyone in Islanderville appreciated his ability and willingnees to go long stretches out of the line-up only to be inserted for spot duty, usually with a specific job in mind.
He's certainly very vocal on the ice and can yap with the best of them. He'll rile opponents up and seems to keep them somewhat honest too.
Unfortunately, after looking like a possible top 3 fighter in the league in his first few seasons, he took a surprisingly clear loss in a tilt against Sam Morin of the Flyers a few seasons back, suffering an injury in the process. Frankly, he hasn't looked the same since.
In fact, I don't think he's clearly won an altercation since then, including two this preseason.
This said, the Isles were over the cap heading towards roster finalization. Something had to budge. Hard to think Lamoriello would have placed Johnston on waivers if things hadn't gone from push to shove. By him being claimed, and in sending Holmstrom to the AHL (still on his ELC and thus, waiver-exempt), the team is currently 1.39 MM under the cap on opening night.