Firstly, my main (not fear, perhaps qualm) is keeping track of marking and status effects. An article at the wizards site already offers strategies for keeping track of these things with minis - and that does seem to present a problem to those of us who are more imagination oriented than grid oriented. This isn't really a big deal, I don't think - if anything the "box" shape of all spell effects should actually make determining what's effected by a spell and what isn't even easier for those of us who can't mentally draw cones and radii. Same with the 1-1-1-1 business. I'm all for anything that eliminates math.
But, I've seen the following a few times, and I just can't see where it's coming from:
AverageCitizen said:
I am afraid of over-focusing on combat.
That's a DMing issue, really, not a 4e issue. Has anything been released that says PCs will no longer be allowed to talk to NPCs, explore, or have a drunken night out? If anything, released information says PCs should be rewarded XP for social encounters, traps, AND combat. I believe a quote even said it would be possible to level up without ever fighting. A changed combat system changes the rest of the world how, is what I'm wondering. How one plays the game is how one plays the game, and I don't see that the non-combat aspect of the game has really changed at all. If anything, it seems to have been enhanced.
I am afraid that 'rogue' means 'damage'.
Rogue means sneaking, stealing, trapping, and backstabbing. Same as always, as far as I can remember. A rogue is indeed qualified as a striker now. But is that really a change from where the rogue stood in 3e? Standing back and firing a barrage of sneak attack arrows into an enemy? Or dual wielding a pair of weapons to really bring the hurt home? But the PHB lite even shows "trickster rogue" as a possible build, emphasizing Dexterity and misdirection, so there are clearly options and alternatives everywhere.
Thankfully, a lot of the fears mentioned on this thread are things that don't mesh with the information we've been given. That makes me think that most of the fears are baseless.

I hope so, at least.