I suppose this isn't a direct question about the tools, but modding in general. Most of what I was thinking of has been brought up already by others, so this is really all I got left:
What do you think about developers who have ignored the appeal of user-generated content? Bethesda and Valve both release these tools and allow content to be spread, but many big name developers in the past few years have distanced themselves from modding communities and not even released tools at all. What do you say to those who have distanced themselves if not hindered the creation of user-generated content? I've been playing Beth's game series since Morrowind, and Valve's stuff with Source and Hammer, and I've watched as other 'big name' developers and publishers have made their games nearly impossible to make maps, mods, and other custom content for over the years, so I appreciate those that are still allowing for this option for those of us on the PC end.
I think a lot of that has to do with how the actual games are made. For example, Valve and BGS games are very moddable because they are modular and very easy to make whatever you want with. However, take a game on the Unreal engine, like Splinter Cell: Conviction for example, to make your own map would be 1000x more complicated. That is modeled and assembled in a modeling program, NOT an editor, so you cant just snap the pre-existing pieces together. Modularity is what allows a game to be modable, and not all games have that.
Also they may not answer that question as it may be getting a bit too 'political', if you know what I mean.