Fighting the level design tools they used gives me a whole new respect for Deus Ex. Man, fuck UnrealEd, even when it's not crashing or silently, mystifyingly failing to actually save the things it said it did. I think as software goes, the UI may be the worst I have ever struggled with.
I have a distinct sense of accomplishment for the three-room map I've created. Three empty rooms, bare-bones textured and lit — two boxes and one half-isocosahedron, two of them linked by a crawlable linking duct with hatches both ends, and a button that raises/lowers a recessed cage from the floor of one room, containing a Delightful Surprise™ gun turret that shoots you for your trouble.
I suppose there are worse things I could be killing time with.