Udk is awesome but its a stripped down version and as far as i know there are scripts or something you arent allowed to deal with without a license and apparantly you have to like really know your shit to get anything decent looking from it ,i dont know but theres 2 big time engines i want to explore thats unreal dev kit and cryengine 3 or versions before 3 , the only thing about cryengine im worried about is content creation for 3dsmax i think you need version 2008 for cryengine 3 but there seems to be cryblender and also a fbx ecporter/importer in dev ..if i could use 3dmax7 or blender i would without hesitation jump into cryengine 3 or perhaps a prev version .cryengine has a nice license model complete engine is free for non commersial and it seems they take 20% roylty on commersial release (theres more to the license options) but it sound very atractive to me ,you get out of the box awesome rendering power and effects like it was a standard and not something you have to add