I have found that I don’t much like rolling on content-generating tables during play. I rarely do it (I would usually rather just improvise), but every once in a while it comes up (like a treasure table in a module that I didn’t bother to roll on beforehand). The box label generator in the Lamentations module Tower of the Stargazer is a good example of this. Rolling those names during the game just killed the sense of immersion, and made it seem like none of the results could possible matter.
Whenever this happens, I feel like it slows down the game and exposes pieces of the machinery that are better left hidden. My most recent face to face group, especially, seemed to become uninterested in content if it looked like the random variety. They wanted to find the “real” content.
There have been a few posts on the blogs recently that have touched on similar issues. For example, Beedo over at Dreams in the Lich House has been talking about how he is using spreadsheets to pregenerate content for his Black City game:
There are also tools like Meatshields! that can help.
The principle is also a bit like vancian casting: you want to prepare the content so that all that is left is the final command word. Note that the content in question can still be loosely bound. Like, you might not know exactly where you are going to need the next barkeep, but having one ready is useful (especially if you are as bad at remembering improvised details like I am).