Ottawa gets: Defenseman Nikita Zaitsev, forward Connor Brown and forward Michael Carcone
Toronto gets: Defenseman Cody Ceci, defenseman Ben Harpur, forward Aaron Luchuk and Columbus' third-round selection in the 2020 NHL draft (previously acquired by Ottawa)

Toronto Maple Leafs: A-
The Leafs get out from under a terrible albatross of a Nikita Zaitsev contract, who is due $4.5 million annually through 2024. And they somehow get a third-round pick in a deep draft for the trouble. That's ... incredible?
It was entertaining to track the reaction to this deal from Leaf Nation, when the first name mentioned in the deal was Cody Ceci. He is, demonstrably, bad. Whatever the opposite of an "analytics darling" is, that's Ceci, with a 43.96 Corsi for percentage last season. Having him on a Kyle Dubas team is like finding out the Vatican is producing the next Marilyn Manson album -- so antithetical to Dubas' established dogma, it's stunning. Ceci is a restricted free agent, but it appears he'll be a Leaf for the next season before going unrestricted next summer.
This is about the money, and the Leafs just cleared a ton of it. They have $11,415,301 open at the moment, and will get even more when they bury Ben Harpur in the AHL. (Aaron Luchuk will be a Marlie as well.) If only there were a restricted free agent who led them in scoring who needed a new contract they could use that space on ...

Ottawa Senators: D+
The best that can be said about this trade is that Eugene Melnyk didn't have to pay bonus money to Zaitsev ($3 million) and Connor Brown ($1.5 million), so good news for Ottawa fans worried about another parking-fee increase.
Senators coach D.J. Smith was an assistant with the Leafs, so he knows both players. Perhaps he knows how to get Zaitsev better than his 49.69 expected goals percentage at 5-on-5, which, again, is something the Senators will have through 2024.
Brown makes this trade a D-plus, either as a valuable grunt in the lineup or as a pending RFA the Senators can turn around and trade. But again: This deal was essentially a third-round pick and a veteran asset (Ceci) for the right to take on one of the most toxic contracts in the NHL.
The Leafs' hand-me-downs continued with news that the Senators had signed forward Tyler Ennis and defenseman Ron Hainsey.
So that's two former Leafs defensemen the Senators have added this offseason. Please recall Melnyk telling Ottawa's CFRA 580 in March that the Leafs are "going to have a tough time winning a Stanley Cup without defense" and that "mistakes were made ... somebody forgot about defense."
Welp.