I have played in a few 'modules', well, at least I was aware of what they were some time into the adventure. And I have had occasion to run a few for others, maybe 'run' is the wrong word, more like turn it into roadkill.
It's been fun any way, either way. Mostly, the problem with modules is that the players don't think like the original writers and playtesters. If the players get stuck at some little obsitcule and can't seem to find a way past it, well, that is where ingenuity of the GM allows for some 'off the wall' idea from the players to accomplish the same goal.
One should try to remember that the modual is designed as a GM GUIDE and not the hard and fast RULE.
As an example, if the players are supposed to open a particular door with a key hidden in a nearby room, and the players just don't seem to pick up on the clues to the key being there ... well find another clue for them. Never let the barbarian use his strenge to break the lock or the thief to successfully pick it. There is a reason for for the key to the door.
But otherwise, well, let the role-play rule, not the rule rule. What ever!!