While there are many things I like about 4e, I'm sorry to say that I truly dislike the layout of the core books. The large, white spaces on the pages simply fail Layout 101 in most of your basic publishing classes. But skipping that, look at the 3e PHB vs. the 4e PHB.
The 3e PHB has colored pages with faint lines on it, evoking the feel of an adventurer's journal. Much of the interior art is a "study" look or sketchy feel, further contributing to the look and feel of some kind of old tome or journal. Even the cover is meant to evoke this theme.
Simply put, the 3e PHB sells itself. And sells itself well.
The 4e PHB does not, IMO. Besides the cold, white pages, the art in the PHB is confusing to me. If you had never played D&D before - by looking at the artwork, what is the difference between a Paladin and a Ranger? The Paladin has a glowing blue sword while the Ranger has two glowing green swords. The Cleric has a glowing mace. So, the differentiation between the different classes through artwork is not done very well. In my opinion, the 3e PHB and even the Pathfinder book does this better.
The large text of the 4e PHB is easier to see, but with the white pages, the overall effect reminds me of a junior-high text book. That is not a snark, understand. Text books take their own layout very seriously and pay serious money for them. However, what sort of look and feel should you be going for in a D&D book?
Finally, the long, long lists of powers look like the charts in my old chemistry text book. Indeed, when I got the 4e PHB, I laid it out beside my old chemistry book and noted that many of the catalog of charts looks very similar. If you were walking by and looked down at both book, they would have appeared very similar.
I'm actually okay with the powers being listed with each class, but the many pages of text unbroken by pictures or graphics makes it dry. It might have cost a bit more, but more pictures throughout would have made a big difference. The 3e PHB saves all of the long blocks of text (the spells) for the end of the book, so the lack of graphics and pictures does not really stand out so much.
In terms of the ability to reference rules, however, we've found that we've had to reference the book very little.

With your powers either written down on a card or on a sheet beside you, we often don't even have to look at our books.