My brother and I have been playing a co-op Be a GM mode in NHL 15, and we've come across two issues that seem pretty big and detrimental to the fun of the mode:
1) You cannot save your changes when it comes to settings for your coaching strategies (line strategies, power play, penalty kill) so we have to go in there in the menu before every single game and change them to be more aggressive to suit our style of play. Very annoying and silly, and seems a pretty big oversight to us. We've looked in the global settings pages (which wouldn't make sense anyway; it should be specific to the game mode you're playing), and in all the settings for Be a GM mode, plus we don't see an option to save them when we change them in the pre-game menu. If they're hidden somewhere else and we're somehow overlooking it, then the menus just aren't designed very clearly or concise so either way it's a pretty big flaw in our eyes.
2) Somewhat related, as a feature you can't save and keep using: We've gotten in the habit of playing set positions, he plays left wing and I play center, but we have to pause the start of every game and go into settings to adjust for this each and every time - again, we can't just set it once and save and have that be the default for the game mode. This one is a little more understandable as one of us could easily play the mode without the other, and it doesn't know that the same two people are playing the game each time, but at the very least we think it should let you do the position lock selection option and the pre-game screen where you choose sides and jerseys and all that. And while we're on the topic... the visual appearance on the screen where you do choose position locks - is terrible. It's a very small and fine font, color-coded for each player of course, but it can be difficult to see. Which is silly... make it stand out.
Other than that - and the fact there isn't an EASHL or equivalent mode this year - we love the game. We're not ones to complain just to complain, so I don't want this to come off that way. We know how much hard work and effort goes into a title like this, and make no mistake: it is quite impressive. Just earlier we watched a replay because a puck rode up our defenseman's stick and hit him in the face, causing him to pause for a second to grab his face and allowing the other team to possess the puck. You see things like that from time to time, but it really does look pretty realistic. Nice. Pick up a copy of the game from Amazon here if you haven't already!