5DII: Level vs. Focus Screen?

There are two big things that I think the 5DII lacks over the 7D: AF sensor and electronic level. Well, I am buying the 5DII and will have to work without these two things.

As a compromise, I am going to buy this focus screen.

Thoughts?

I am someone, who when I shot with my EFS 10-22, would sometimes get things off kilter by a degree or two. Since I can't install an electronic level into the 5DII, and I am hoping this might be a good compromise solution.