4E had its ups and downs for me.

I liked that it gave martial classes equal billing. I liked how it simplified a lot of things from 3.5e (things that 5e gets credit for, no less).

There was some weirdness, though. They latched onto the grid-and-minis based gameplay a little too much in the book's descriptions, to the point where the default distance measurement was squares on that grid. They pretty much took aggro-control directly from video games where that stuff works, and transplanted it onto D&D where the DM now has to really stretch to justify that monster suddenly attacking the big burly tank instead of the squishy, easily-targeted Wizard just because he's marked.