I think this is a great dsicussion!!!!
IMC I have been accused of both leading the PC's to much and not leading the PC's enough, both by players in the same group. I have to admit, I understand where the frustration comes from.... "let me splain".
My current campaign is an epic campaign, planned for levels 1 through 30. This is a very very broad range for a single campaign, but I have developed a method (successful so far) to make it easier to work with.
First, I view the entire campaign as a series of books or TV mini-series (a la Babylon 5). I use terms closer to books, and as such the campaign is split into books and chapters. Each chapter is generally one "adventure" while each book is a mini-campaign. Each book ties back to an over-arching plot line for the entire campaign.
The over-arching plot line has been drawn out in minimal detail for the entire campaign. Basically, BBEG has such and such a background. BBEG is aiming to get to such and such a point. BBEG is at such and such a starting point when the campaign begins.
Now, within each "Book" I lay out the details of what is happening in the world at that point. For example, the first book was entirely concerned with a Major Orc invasion of the country the party is from. That invasion, of course, tied back to the ocer-arching campaign, but the goal was more of an introduction or prelude to the campaign as a whole. (sort of like Wheel of Time by Robert Jordan (the first book, not the series)).
Now, I then split each "Book" down into chapters where a certain line of events will happen. I then toss in the players and let them react.
At the end of every chapter I go back and match the actions and reputation of the PC's to the outline of the "Book". Based on this, I can make changes on a chapter by chapter basis, be they minor or major. (Damn, that troublesome hero just foiled my plot to only sell red jello and banish the other colors of jello from the world!!!).
Because I do not put restrictions on what PC's are in the game, and work to create plot hooks for new races/characters/classes, I was accused of not being controling enough. Also, because I do not restrict the PC actions within the game, I was accused of not being controling enough.
Now, let me futher explain that I do not believe in leading the characters by the nose, but I do believe in world continuity and in reputation settingfuture actions. This really hit my players as they came to the end of the first book. Because of my setup, the players, upon entering the last 2 "chapters" of the "Book", pretty much had pre-scripted the outcome of most encounters. They had already, through past actions, determined major NPC reactions to them and such.
I carry this longterm affect out to the over-arching campaign as well. When past NPC's reoccur, they already have preset reactions and thoughts on the PC's.
Lastly, as the PC's finnish one "Book"and move into the next "Book", I review the actions and results of what has happened in the book and then apply those affects to the over-arching campaign. This determines where the overall campaign is still headed, and allows the BBEG and other campaign entities to modify thier actions in the future. It also provides basis for future "chapters" and "Books".
I hope all that makes sense.
Bill