There are some things added in the MM that make things clearer (stat wise, ECL wise, etc etc).
The Wood Elves took a hit though...for those of you that play them. They now have a stat adjustment of +2 Str and -2 Int. Not that ungodly racila stat adjustment that they did have. I like this better than it was before personally.
The DMG has some more detailed information on towns and generating random encounters. Heck...there's even a random URBAN encounters chart! HUZZAH!!
There's a few more magic items and abilities. There are some clarifications with how magic items stack. No longer can someone wear a suit of armor and a magic robe. I find this to be quite interesting. Lots and lots of charts...all easily readable. I like the Mystic Theurge. So what if they get "one of each" spellcasting class. The Archmage was clarified, the Duelist took a slight hit in AC, and the Horizon Walker makes me wonder what the hell they were smoking.
The PHB at first looks like it is trying to squish things a bit. Where the 3.0 book seemed spread out more in the Classes chapter this one seems a bit compact. All the info is still there, it just seems bunched. This is just a "future graphic designer's" look at it. There were some surprises to the classes. Wizards now get Decipher Script (about time!). They slightly detail the auras surrounding Clerics and Paladins (for those who cast "detect (alignment)" spells). The skill list is still there, but with the "class or cross-class" chart you think they would have made up another letter besides "C" to use. Like maybe "C" for class and "X" for cross-class. There are no more "class-exclusive" skills which I find somewhat disturbing when it comes to Use Magic Device. It's just the fact of seeing Sorcerers with High Charisma scores going around with Cure Light wands and feats like Skill Focus(UMD)...which now provides a +3.
So a 1st level Human Sorcerer who has an 18 Cha and spends 4 points in UMD, chosing the SF(UMD) feat along with Magical Aptitude (+2 on Spellcraft and UMD checks) gets a +11 on UMD checks...AT 1ST LEVEL!!! While I think it ads something to the game I see it getting abused. Even on the other end of the spectrum with high Cha Clerics and Paladins with Fireball wands or something. If they were going to make UMD a non-exclusive class skill why not make it a class skill for Clerics taking the Magic Domain? Of course that would negate the Domain power somewhat...but anyway.
There are some changes to spells and what schools they belong to and what level they are. For instance...Burning hands is now an Evocation Spell. Produce Flame is a 1st level Druid spell...and etc etc. They list spells from some splat books (Tome and Blood, etc etc) in here as well. They also have marked which spells require material or other special components not normally found in a spell componet pouch.
I'm not sure how the weapon sizes will work out...should be ok. Why do it though? This seems like something that shouldn't have been messed with. As far as I'm concerned the damage a weapon does it based on it's mass, not it's size. The mass of the metal it takes to make a longsword is different than that of a short sword. So why make a "longsword for small characters" listing? Maybe I'm missing something here...but it'll be ok.
Armor has it's own AC, and Shields have their own AC...which stack. a Magic weilding PC can no longer weild a shield and cast the spell Shield.
I haven't read the combat rules completely yet...but Lightning Bolt (used as an example) is now a 120 ft line. It doesn't end until it hits a barrier it cannot pass, or the end of it's range.
All in all I think this is a very fine revision to the game and worth every penny.
I know some of you may not feel the same, but hey...alot of people didn't like 3.0 either.
anyway...that's my take