UDK is Unreal Engine 3 – the complete professional development framework. All the tools you need to create great games, advanced visualizations and detailed 3D simulations. The best tools in the industry are in your hands.
I rate this engine a 9, it is very good looking, well advance and perfect for making 2012 video games, I was going to rate it a ten but I have seen better looking engines like my ShadowEdge Physics Engine, the Game Engine used for Call of Duty: Black Ops (IW Engine) and the improved RAGE Engine used in Grand Theft Auto V.
To me, the Unreal Engine 3 is still great but has been around for awhile now and newer engines are being made and are surpassing the UE3 graphics.
I use UDK at University I've Recentley created a small kismet example map for my course, it's a fun and creative program, featuring some cool little utilities such as the good old brush with additive and subtractive geometry,and the awesome kismet and matinee animation so simple and easy to construct, Fill out your map with lovely textures, imported into UDK and applied by creating materials which allow endless tweaking!!!, I am yet to unravel the mistery of Unreal Script, but thats just me VS coding and such,
LEVEL DESIGNERS AND GAME CREATORS >>> UDK <<<< xD