-Fear: Intelligence will not do anything.
It doesn't do a whole lot, but it does something. I would've liked Intelligence to add to Initiative instead of Dexterity - reflectinig your mental ability to figure out the situation. After all, after the first round initiative doesn't have much to do with your reflexes.
-Fear: That it will be difficult to design for because a) there's only so much you can do and with hundreds of powers in just the first book, a lot's been done, b) creating something like a class will need thousands of words worth of powers along with the class itself.
I don't think either parts of this fear are true. Designing a class is certainly more involved than it was in 3.5, but that's not necessarily a bad thing.
-Fear: Many powers will just be copy-pasted to create new classes because there exists no system for classes sharing powers.
This is happening in amateur creations, but again it's not necessarily a problem.
-Fear: That combat will be just as slow as it is in 3.5 because people will still need to keep track of finnicky bonuses/ongoing effects.
It's faster, but it's certainly still finnicky.
-Fear: That the social combat system will kill role-playing.
Not a problem, especially since it turned out to be so rudimentary.
-Fear: There will be too many powers per character to keep track of or, conversely, there will be too few so each character will play through each combat the same way.
Neither of these are true, but I think there are definitely elements of truth in each one.
-Fear: The GSL will be too limited and restrictive so innovation is stunted.
YES! Definitely a problem.
-Fear: Powers are unnecessarily limited (e.g. rogue powers restricted to certain weapons), and the solution will be a deluge of third-party products removing these unnecessary distinctions.
Rogues are pretty much the only class that is limited in this way, although others have problems - for example, multiclass characters and using implements from two classes.
-Fear: 3.5 is so robust too few people will convert over so that D&D is no longer profitable.
Not the case or, at least, not the case just yet.
-Fear: The skill list is too pruned.
Not a problem, for our group at least.
-Fear: Class restrictions (such as set trained skills and weapon proficiencies) will result in many new and alternate classes, feats, paragon paths, alternate class features just to remove restrictions that should not exist in the first place.
Not a problem.
-Fear: The quality companies that refuse to convert to 4E will die off.
We shall have to wait and see, but Paizo at least seems to have secured its existence.