I posted a rant the other day, and instead of posting a comment I'll make a post out of it. Wild ranting is more fun, but since I did have a point I will put it through a bit clearer.
So, well, I was ranting and thus making the arguments walk that extra mile. But, I think I still have this idea about being a DM and being creative.
If you feel you have to stick to the book, and thus limit yourself to the extent that you feel stumped when not all your work is done for you, I think your style of game mastering could use some tweaking. In order to make a "canned" adventure work for you, you will not be able to just pick it up and run. If you could, computers could do it better.
Being a DM is, in its essence, to be creative and adaptive on the fly. Not even saving some time with a pre-designed module will change that. It's not easy, but it can be done. I keep fighting with it.