Good: streamlined game mechanics, easy to run monsters, less prep time for DMs. (did you see the new stat block?!?

)
Bad: the fear.
The fear that it is too demonic (half demon races, demonic classes, demons and devils for opponents - what does the second 'D' stands for in DnD?);
The fear that it is a flashy superhero game (all that 'anime' talk - and don't get me wrong, I like anime);
The fear that DDI and Gleemax become somehow 'necessary' for play (even though they say it wont

);
The fear that everything is related to hp ("I do a war cry to intimidate him", "ok, he loses 3d6 hp"

);
The fear that per encounter/day powers seem too much like vancian magic ("I'm sorry Bob, you've used up all your power attacks for the encounter, but you can still use cleave 4 times a day" "what the!?!"

).
The fear that everything is about combat and that these roles dictate how you should play the class (if I want a pacifist wizard college professor, I want a replacement for 'wizard strike');
The fear that powers make the game more complex for every class (It was easy playing a fighter, wizards weren't - they used to say spellcasters were for 'advanced' players; I like options, but begginers will find it hard to decide between 13 abilities they don't know well);
The fear that PHB7 becomes core, but not SRD material;
The fear that there won't be an SRD;
and the fear that these and other assumptions are true. :\
We just don't know enough about these 'cool' changes they are doing. They keep saying how they fixed everything that didn't work, but don't show us anything significant. We can only wonder... and fear.