Again the 3 questions. All things being equal and assuming no other negative impacts on gameplay.
Is having a load time better than not having a load time? Is FO3 better off having a half second delay to accses and exit the UI better and more enjoyable than not having the delay?
You mean pulling up the PipBoy? (Load time? Is that a console thing? I just have the animation)
Honestly, didn't really bother me, since it fit the theme & concept of the game. In some other game, it might be annoying.... depends on how long the animation is and how often you end up doing it.
(I will say that the "you zoom in and out on a 3D map" thing for Skyrim sounds a little iffy.)
Is removing hotkeys(for maps & quests,etc) a good idea, in other words in FO3 UI better off with out them?
F1/F2/F3 for the three main sections of the pipboy? Didn't have a problem with that, it seemed like a good amount of hotkeys. (Were there more than that in Oblivion? I generally just use Tab to open the menus in that game....)
Is being able to see more information(grid or list) better than less, in other words is FO3 better off only using half the screen for the UI?
Again, I didn't have any problem with the pipboy interface. It fit the style of the game, and I didn't particularly feel any "OMG, they could be using more screen space!"
And thought experiments, imagen there is a half second delay when ever access thing like your tabs in your browser, exiting, bookmarks,etc any thing that before was instant.
2nd, resize all your windows you normally use to half size like FO3, so your browser window cut down the visible view by half. Now see how long before it bothers you?
Repeating again, I didn't have any real issues with Fallout 3's interface. And like I said, it would depend on each individual game or program I use - different window sizes for different tasks is pretty normal for me.
And no - slow performance in tools that I'm using to do daily tasks would be annoying. Thematically "realistic" and "immersive" (HAH!) things in a game, that don't cause any real problems? Not the same thing. (You'll note that I'm not considering the Fallout 3 interface to be "slow". It does not have performance issues - it was deliberately designed to work that way. Slow performance in Firefox or Photoshop wouldn't be a stylistic decision - it'd be badly optimized software and/or incorrectly weak hardware.)
If something reduces or harms usability, it's a problem. I had no real usability issues with the FO3 interface. It worked for me, and it worked fine.
(An example of poor design harming usability - Borderlands interface font was a bit too big, because it used the console text for the PC interface. This meant that you couldn't see the fifth line of text on random weapons that had lots of additional powers. This, is a problem.)