Many remember the light blue maps that came inside of B1 - Search of the Unknown, B2- Keep on the Borderlands and many other early modules. While there were some detail on those maps they were basically gridded rectangle in a sea of light blue. I acknowledge that the minimalist format has an appeal to many I think the format pioneered by Tegal Manor and Harn really adds value to a module that text only doesn't do.
Let's look; first Tegal Manor
The Tegal Map is just packed with information about the different rooms and hallways.
While less on the map text the Harn style makes up for it in detail. You can look in each room and visualize the contents. Those of you want to look at in more detail you go to Lythia.com and download Tashal Eastside City Block. For even crazier example you can download the Tashal Upper Eastside.
Often the most effective presentation and books are those who combine good writing AND good graphics. These two map styles in combination with the text makes for a superior module than either alone. Many of the professional maps I do have little "bits" inserted to help the referee flesh out the scene without having to add a lot of text. One thing I need to work on is adding some verbiage, like Tegal Manor, to give the referee a sense of what the environment is like. I love how various areas in Tegal Manor have text like creaking, hissing and so on.
The one caveat I have is that I don't like the photorealistic maps that are somewhat in vogue. Don't get me wrong I think they make for great battlemaps. However for use in the actual book I think the b/w greyscale (or minimal color; 2 or 3) is clearer. The use of full color photo realism often results in muddy looking maps on the 8.5 by 11 page.
I also think the Harn maps goes a little too fair in applying various texture files. Too many will also muddy your pages. In the end you have to practice and try various approaches until you find one that works best.
A map that successfully combines all these elements is one that really earns it's keep.