I don't know why you find it so hard, man. As far as editors go, it's one of the easiest I've ever used; and I've been modding shit since the days of Starcraft. You have a wireframe brush that you can resize to whatever shape you want. You use this brush to add objects and subtract space from the game world.

Want a box? Make the shape of a box and click the "add" button. Want a hole in that box? Simply make the shape of your hole, put it in to the box and hit "subtract".You can make ANY shape you need, and it even has pre-built shapes like stairs and basic geometry for you; everything else is literally drag and drop + context menus. It's as simple as you can get!

Source is alright, but they are living in the past with their archaic editor. Having to make sure all of your walls are pixel perfect to avoid "leaks" and other memory related bugs; having to compile and load an external program just to test a small change to your level; not having access to all prefabs available in owned source games. The list goes on, which is sad, because Source is an awesomely versatile engine at the end of the day.

I pretty much recommend everybody to at least try it out and go through a couple of tutorials on the Unreal website. It will take you 30 minutes and you'll be building your own levels in no time.

FYI, You just compared a SDK usage number to an actual game sales number.

I already installed it, but haven't had time to mess with it, i'm learning the Unity Engine right now

lol