While Gears Of War didn't invent wall cover, it did popularized it. Multiple games now use third person wall cover. And for practically every genre it is associated with, it is awful for the most part.

A good example is a game I was playing recently, Deus Ex: Human Revolution.

With in the games skill tree, the player can spend experience points that allow a greater sense of awareness. Agumented vision that shows enemy through walls. Pinpoint markers show enemy position beyond the boundaries of wall.

This mostly becomes moot however, when the player can simple glue themselves to a wall, and have a full 180 degrees viewpoint from a third person perspective.

In the case of Deus Ex: Human Revolution, even though it does seem to fit the gameplay and outright makes aspects irrelevant, it is in their. Most likely on the basis, thats it's a popular console mechanic. This is outright bad game design in my opinion.

For practically every action game that uses this mechanic, the AI cannot cope. In Mass Effect the AI will blindy run towards you regardless of you being unhittbable. It doesn't take your wall cover into account For supposed "tactical games" like Rainbow 6: Vegas you once have a full 180 degree view without any limiting. Simply pop up your head, fire, duck. Rinse and repeat. The advantage third person wall cover gives, is huge. The AI for the most part, cannot cope with it and the mechanic itself (to me at least) is outright boring. When I think of action games, I think of something visceral like MDK. Doing strafe circles around dozens of enemy. Sitting in a corner, popping my head up and down with bursts of fire, is practically the exact opposite of visceral.

It seems to be me, this mechanic would work much better as a first person only mechanic. Without the ability to pull out to third person for a full 180 degree viewpoint. In a game such as "Red Orchestra 2" using wall cover delivery limits what the player can see giving disadvantage as well as advantage. Aside from not having a full view in front of them, they also lack side and back views. This limitation makes the tic-tack-to of battles far more interesting than they would if you could simply pull out into third person.