Good compared to most games, but not when compared to the rest of the series (no-spoiler review)
Long gone is the feeling of freedom that came with the first game. While there were stretches where things like driving became boring and repetitive, there's no question that the game presented the galaxy as an absolutely massive and complex place open to exploration. Rather than fine-tune this approach, the second game did away with it altogether but made up for this by increasing the depth of the characters and side quests.
Unfortunately, Mass Effect 3 feels even less free and complex than its predecessor.
It's just missing something... a bit of polish that was left off. Small bits of dialog or details that peppered the previous 2 games are just not there to the same degree, leaving the impression that the developers either didn't have time to create the same level of detail or were just relatively lazy.
Case in point: James.
In previous games, team members each had a fascinating backstory that would eventually give Shepard the option to lend a hand and form a stronger bond with that team member. Even before the loyalty system of Mass Effect 2, the first game still drew you in to each team member's own journey in some way. By contrast, James is a fairly bland tank character who wants to move up in the alliance ranks. No real backstory or side quest is given, and I never felt connected to James (or to Javik) as I did with other team members.
Because of this relative lack of detail, the world is less a place for exploration and more a place to just run through as you tick off things on your to-do list. Perhaps this is why the combat of Mass Effect 3 seems like a never-ending grindfest compared to the previous games. The amount of fighting is not the problem at all. It's really a matter of pacing. If the fights were broken up more by opportunities to do something else, find out more about a team member, or learn some fascinating new insight into the universe, it would have been much better. Instead, you're just left with a formula of fight, activate quest trigger, fight, activate quest trigger, fight, leave location in shuttle. Repeat ad nauseam. Granted, it certainly did not feel this way all the time, but there were several points when it did. The previous 2 games seemed to balance this much better. Another reviewer has commented that the game eventually feels like a third person shooter with a conversation mod bolted on, and I think that sums it up pretty well -- particularly the later stages of the game.
The Galaxy at War system is an ill-considered approach to gaming. While I commend BioWare for coming up with creative ways to tie in the game with other activities on other platforms, it's very poorly executed. Contrary to assertions made by the development team, it is not possible to hit the upper threshold of war assets required to trigger all options/cutscenes without playing a multiplayer game or one of the applications designed for iPhones/iPads. It's completely unnecessary and should have been left out altogether.
The ending is quite poor and seems to have been thrown together at the last minute. No attempt is made to bring closure to any of the immense number of subplots you've been involved with over the past 5 years. Any care you've taken to smooth things over between people, groups, or entire cultures are completely brushed aside and ignored, apart from raising your number of war assets. But no subplot is really tied up at the end with nice bow. It all ends rather abruptly.
Bioware's ability to tell a good story and the sheer enjoyment of the galaxy they've created is what has led me to rate this a 7, despite these significant shortcomings. It's an adequate conclusion to the series, but ultimately a let-down. It could have been so much better with another month or two of development.