Bruins fan. My experience with Julien is as follows:
If your team is below average he will bring them up to an average level. If you have standout talent on the team he will not use it well. He came to Boston after the offense had fallen apart other than Bergeron and rebuilt it up to a decent level over 3 years, but played a very conservative trap style game that resulted in a lot of low scoring.
He did, however, create the emergence of Tim Thomas and gets some credit for that. He also prevented a very slow, shallow, weak defense other than Chara, from being exposed, by using the forwards to cover part of the defensive assignment. In other words, at least in Boston, he coached well to the strength of a large, physiical, but not particularly athletic team.
the problem is that as the team got faster and more athletic Julien didn't adjust his style of play. Like, at all. Chiarelli would make moves to make the team smaller and quicker and Julien was still giving them assignments as if they were big and bulky like they were 3 years prior. The man does not adjust. He's a very stay-the-course coach and that's not what you need on a new franchise that needs to evolve rapidly.
My bottom line: Julien is a coach you hire to squeak an average team into the playoffs and win the occasional game. He'll get youu some extra playoff revenue if you're a borderline team. For a bottom feeder, he's not useful and for a high skill team he'll hold you back in the name of team D. He's not as bad as he looked in his second stint in Montreal, that team is recovering from a period of utter dysfunction right now, but hes' a coach you bring in for a specific reason and the Kraken may or may not even be in that position.