i just thaught i would post my view on UDK.
udk has some great features

Level Editor
Terrain Editor
Unreal Matinee (camera cinimatics)
Speedtree (fast tree modeling program)
Kismet (visual scripting system)

im using it at the moment and think if you wannt to make a good shooter
udk is the quickist and easyest way to do it. im loving the matinee system .it makes cinimatics fast and easy. the editor is solid with a nice gs subtracting.

one thing im not shure about is the scripting.
can you put scripts on to it? whithout kismet?

Thanx xonath