I certainly try to, after all, that's the beauty of published modules. For a one-shot or novelty session it's pretty much straight out-of-the-box. Those that take place in my main campaign world will, of course, have names and locations changed to fit. But I try to keep as close as I can to the original text. After all, somebody poured a lot of time and effort into it.
So I try to keep changes to a minimum. I've noticed that I make any changes (other than the most superficially cosmetic) reluctantly. In the back of my mind, a little imaginary man counts every alteration and, when some arbitrary Magic Number is reached, decides that the module is now too far from it's original concept. That means that it gets scrapped; broken down for parts or combined with bits of other adventures. Wow, insight. I'd never articulated the little man and the Magic Number before. I guess one could say that I respect the "dignity" (the best word I can come up with) of the adventure and treat it accordingly.
All this is probably due to my DMing style. I encourage imrov and player input. For example, introducing PCs at the start of a game, I will say things like: "Evvie the elf is a junior member of the Messenger's Guild. Another member has had a secret crush on her for years. (Turning to Evvie's player) What's his name?" or "Among the gypsies singing and dancing, you see one at the edge of the firelight, trying to get your attention. What's he want?"
This gives the players a real connection to the setting, and it provides me with unexpected twists and turns. Much fun. But it exacerbates the havoc that players wreak on plotlines and such. So, with published adventures, it's just easier for me to run them straight as written, with no major changes to keep in mind.