Strong as an Ox
I decided a little while back to switch from my own home-grown XNA framework to using an existing one.
I had a look around but couldn’t find one that met my requirements, I was after a solid, modern, game engine that wasn’t tied into a specific type of game.
Most of the engines I came accross seemed to be using the old shove everything into one scene graph method, until I came across the Ox Game Engine (http://www.codeplex.com/OxGameEngine/).