Generally, I like the move. Even Leiweke has a boss - the MLSE board. All hockey execs do.
A hockey guy, Shanahan, will evaluate the performance of the GM - not a bad thing (think of that compared to Peddie ...) . A hockey guy, Shanahan, can do some of the ribbon cutting/PR stuff/MLSE board stuff letting the GM focus on acquiring the hockey talent.
I liked that Shanahan didn't come with a preset notion on how a team should be built. He sounded like he'll evaluate what they have and be flexible on the best path forward from the talent they have. That is better to me than Burke's approach of "I want this team to reflect my idea of a model - truculence, testosterone, etc" because that takes more work to assemble that from where they were and therefore, it is less likely to be achieved. In other words, there is more than one way of going about it and Shanahan is wisely open to that.
As for Nonis, he's been kind of screwed trying to make Burke's retooling effort work (not that he isn't responsible for a bunch of that). It's a tougher way to try to win as he doesn't have the fruits of a true rebuilt young core to work with. Now he's kind of stuck with all the contracts he's done to tie up a core that struggles to make the playoffs. It's hard for me to imagine how he can ever fully rebound from that. He can get them back to the playoffs but he'll be hard pressed to get them into a parade any time soon.
Shanahan probably realizes that and is going to take his time coming up to speed on what they have and what they lack while Nonis flails away ... and Shanahan lines up his eventual successor.