My first version of the game is still sitting on my shelf in a little white box. I started playing in 1977, and have gone through many... though not all of the changes. As the game has evolved, there are some good and bad things that have happened, and this has continued with the latest version.

First, let's examine the new books. The core rules books, the Player's Handbook (PHB), Dungeon Masters Guide (DMG) and the Monster Manual (MM) are available as either a boxed set or three individual books. They are the same size as has been common for the last several editions and are printed on nice paper in color. Color is used in interesting ways in the books to convey additional information. The use of color for this purpose is nice. The art is excellent and is nicely printed. The books seem to be well made to stand up to the rigors of use. The boxed set is quite nice, but I question how well the slipcase will travel.

Examining content, we should probably start with the Players Handbook. The first thing I noticed is that several classes have been removed from the core set. Rumor has it that there will be follow on books to add these classes back in, but this is going to slow transition in my game as I have players using some of the omitted classes. I am pleased to see that an index has been added, but the quality of the index is not good. I consistantly had to bounce between the table of contents and the index to find things. Admittedly, a good index is a lot of work, but given the price of the books I expect better.
We also find that a couple of new races are added. I find each of the races interesting, but they seem to be very setting oriented. More about this later. Spells for the spell using classes have been reorganized and the magic system has been made much more powerful. This may introduce game balance issues for some games as the magic using classes are now more powerful than I've ever seen them. I will have to do some playtesting to see how this is going to work in my game. The skills have been trimmed, and the power of skills has been reworked. I'm not sure about this either, as it will certainly change the way things work. In some ways this will simplify play, but it does limit what a Player Character (PC) can do. This isn't going back to the AD&D 2e level, but it isn't as rich as the 3.5e set. Overall, I find the organization of the material better than 3.5e or 3e, but not as good as 2e or 1e. There has been an attempt to group things together by class, but this breaks the book up in ways that make the information about all classes more difficult to find.

The Dungeon master's guide is quite a bit lighter than previous versions. I did find that there was more information about how to be a DM, and this is very  welcome (or will be to new DMs). I still miss the quality of random generation tools that was present in the 2e guide though. The set of special magical items in the DMG has been seriously cut down and seems once again to be very setting specific. It feels very much like a lot of the information is being moved to supplemental books. I'm not averse to this, but the retention of setting specific information while removing general information is not my preference.

The Monster Manual has fared the worst of the three core books. The choice has been made to more strongly class monsters as evil creatures and to only include those evil creatures in the MM. I find this to be an overly simplistic world view. I don't mind if some campaigns do this, but to make this statement and then enforce it by removing common "good" monsters is poor in my opinion. This book did not get the benefit of an index as the other two books did. Most of the book is an alphabetical listing of monsters, so the index and table of contents would be more similar in this book, but the information about all monsters and the appendix information is very poorly indexed by the table of contents, and generally the overall data quality of the book is poor. Pictures in this book are not as good as in previous versions as the monsters are often shown in groups such that it can be very confusing to know which member of the group is the monster you're interested in. The quality of the art is good though, and my complaint is not about the art so much as the organizational problems. Overall, this is the worst version of the monster manual since the white box pamphlet.

Finally a word on the setting specific stuff. It is obvious that Wizards of the Coast is promoting a new game setting along with the core rules. In previous versions, although all setting material could not be completely divorced from the core rules, there was a consistant effort to have the core rules be just that, core rules and for them to be setting independant. The inclusion of so much setting depenedant material hampers those of us who have not used purchased material as our primary world material. The level of setting inclusion and the interferance I expect it to make in my campaign setting is high enough that I will be re-evaluating the core ruleset that I will use moving forward.