ok now that the season started who actually won this trade?
If Murray can keep up this level of play and stay healthy, it is obviously a huge win for Toronto to get a Vezina caliber goalie at 4.7M x 2 years.
Murray had streaks of very strong play in Ottawa where he would average a .915+ save percentage over multiple games. He would then get hurt, and lose all his momentum. Until he shows he can remain healthy for long stretches of time, I am skeptical about him.
Because Ottawa is a budget team, you have to look at what they gained by proxy. Ottawa paid a 3rd+7th to free up 5.25M this season and 6M next season. They spent 3M of that on Murray's replacement, Cam Talbot. Ironically, Talbot was injured in training camp. Which is what the Senators tried to avoid by moving Murray. Since returning, Talbot has provided more consistent play than Murray did for his entire tenure as a Senator. Similar to Murray, I won't be sold on Talbot until I see a larger sample size of strong play.
Keep in mind, the Senators got Talbot for free. Gustavsson was a sunk cost who was likely to end up on waivers. If anything, he was a detriment to the Senators since he was on a 1-way contract and the Senators have a budget to uphold. With that said, he is playing well in Minnesota as their #2 goalie so it is possible he would have stuck with Ottawa.
If you analyze all the related deals, Toronto traded Mrazek, and the 25th pick for Murray (@ 4.7M) the 38th pick, and a future 3rd and 7th round pick.
Ottawa traded a 3rd, a 7th, Murray, and Gustavsson for Cam Talbot, 2.25M in salary relief, and 6M in salary relief next year.
If Murray keeps playing this way, the Senators are going to regret giving Toronto a franchise goalie. With that said, the likelihood of Murray remaining healthy is low based on his injury history.