I liked it, played it a good bit, wasn't much to it though. The way you are putting it is like half the game is based around it.
Half the game is an understatement...
Things like Counters, Melees, Coup de Grace, etc... CORE gameplay features but ironically things most casuals won't even think about doing in a casual run of the main campaign, and indeed have no reason to even try in the campaign.
And that's exactly why opinions are split I feel.
A good portion expect it to be a Gears of War shooter, which is why they're not appreciating what the gameplay can really do.
The other portion sees it for what it is, and can enjoy the game.
Case in point -- went back to Campaign recently after pretty much learning the Mercs gameplay to a good level. It was so much better the second time. All the 'difficult' part turned out to be just me being a mercs noob.