There seems to be 2 schools of though on Module Design, although I maybe wrong, this is how I see it. There's basically the new school and the old school look/feel. The Old School look for me harkens back to "Keep On The Borderlands" its straight forward, typed fonts, bold sections, easy to find, the whole damn thing is in black and white(including the limited graphics), and the cover has a very similar vibe to all those great modules that came out in the past (with the little triangle bit on the top left side with the module number or whatever there).
The New School is glossy, digital graphics, parchment type backgrounds for the paper, sexy fonts, easy to read and find certain things. Some of the graphics almost have a water color feel (inside of some pathfinder books).
Obviously there are variations on the two above, and there is a lot of DIYer's out there that push those boundaries and change things up a bit, which I adore.
For me it never comes down to "Judge a book by its cover", however I'm sure that happens for some people. Does the look of the book's cover change your view on wether to buy it or not?
I was toying with re-working "Caverns Of Ugard" to be a little more New School looking, and while it is sorta turning out, I am still quite happy with the original old school feel. I am currently working on my enormity project, and I am quite sure that its going to have the old school feel, B&W everything. I quite doubt that I will afford any graphics for it, but I do plan to do some pencil drawing's to highlight certain pieces of equipment etc. I may even draw up a little whispy footer for all the bottoms of the pages.