I like the way weapons are being handled. Small characters can use so much more--so less size-based damage penalties--and can still use big weapons if they absolutely have to thanks to the Heavy property. The main drawback is what happens if a Medium character uses a weapon sized for a Large creature? It would probably be more elegant to just make a globally applicable disadvantage/attack penalty rule.
Other than that my only real complaint is that the Bull Rush maneuver is limited to pushing around creatures your size or smaller. I think that you should be able to burn Martial Damage Dice to beat back a bigger foe. At least one size category so halflings could get more mileage out of it (after all you can affect a bigger creature with Trip in this manner).
One the topic of maneuvers, I do not like that Volley and Whirlwind attack have you use the same attack roll for every target. That makes it pretty likely that you will end up getting and all-or-nothing result. I would stick with the 4th Edition model of multiple attacks and one damage roll, especially if you are trying to shave off time from dice-rolling. Oh, I would also allow Rapid Shot to be used with any ranged attack.
Shifting gears a bit, one of the complaints that I have heard is that fighters deal "way too much damage compared to wizards", which actually means that the fighter, monk and rogue deal way too much damage compared to wizards because they all have the same attack bonus, Martial Damage Dice, and Martial Damage Bonus progressions. It seems kind of odd that the fighter, a guy who is supposed to be very good with weapons, ends up being on par accuracy and damage-wise with half of the other classes.
Anyway, a 1st-level fighter packing Strength 16 and a longsword will end up dishing out 11 points of damage on average, and they can do this all day. A 1st-level wizard, on the other hand, can reliably zap enemies with 5.5 points of damage, whether from a distance (ray of frost) or up close and personal (chill touch or shocking grasp). The same wizard can also, twice per day, open up a thunderwave to the tune of 9 damage with a push effect, or 10.5 with burning hands.
So basically even the wizard's per-day guns end up dealing slightly less than what the fighter can do. Their only saving grace is that they can affect an area and will always deal damage, which despite being a ridiculously paltry amount of 4-5 is still sufficient to clean house on centipedes, goblins, commoners, kobolds, and similar level 1 fodder. So...maybe not so bad?
Well, at 7th-level the gap further increases between the two classes: a 7th-level fighter's average round-by-round damage becomes 26.5, while the wizard only manages to eke out a whopping 11, or 21 with the one daily spell she has available. Again, area of effect and it will always do something, which in this case means shaving off about half the maximum hit points of a lot of the available level 3 monsters I saw in the Bestiary.
At 11th-level things seem to change a bit. The fighter clocks in at 40.5, with the wizard falling further behind at 16.5. However with a thorough application of chain lightning (max targets, all failed saves) she can dish out 105 damage total, or 52.5 if they all make their saves. Given the range and the fact that do not have to worry about friendly fire, as long as you have at least two targets (each creature can be hit by up to two bolts), this should not be hard.
One problem is that the wizard only gets to do that once per day, or two if she took Scholarly Wizard. After that she ends up relying on lower and lower-level magic. The other is that I have no idea how heavily this will matter given that stat-scaling all around has been flattened out, so unlike 3rd Edition the wizard will have the exact same chance of hitting a monster with any given spell, and unlike either 3rd or 4th Edition lower-level monsters are intended to remain viable threats given sufficient numbers, which is precisely where area-effect spells can really shine.
One point in the wizard's favor is that she now has more flexible core-spellcasting than she has ever had before, so you do not need to choose how many of which offensive spell you want ahead of time. Of course, none of this factors in the usefulness of control magic (cause fear, charm person), utility magic (invisibility, fly), and save-or-screws (sleep, hold person). I plan on giving a few wizards a shot just to see fun and useful they are.
On a similar not I think that all wizards should be able to use detect magic at will, as being able to detect the presence of arcane energy seems like it should be the first thing they learn. On a similar note given a short period of time they should also have a chance to read magic that fits their style. So an evoker should be pretty good at determining if the magic surrounding a door will unleash a gout of fire if opened, while an enchanter might be good at discerning if someone is being magically compelled (and if they cannot, they should have another, perhaps better shot, given more time to properly research it).
I am a fan of recycling class features when they make sense. I think that martial maneuvers worked out great for the rogue, and could see them for the ranger and warlords. Similarly skill tricks seem like that they should be available to most classes, just on a restricted basis. So rogues get their Charisma-based stuff that lets them distract enemies, boost initiative, and fiddle with magic items, while fighters could quickly force open doors (as a call back to bend bars/lift gates). I mean, why cannot a fighter Climb Sheer Surfaces, Display Deadliness, or Great Fortitude?
Actually, skill tricks in general seem a little strange. You can use Strength to climb and you can gain training in Climb for a variable bonus. If you have Climb Sheer Surfaces, you can make a Climb check sans skill die to climb further. I think ability scores should have skill-like applications that anyone can try, skills should give you flat bonuses with more focused areas, and skill tricks let you break the limitations or try even stranger things.
For example Intelligence and/or Dexterity could be used by anyone to try and disable a trap. Like, Intelligence could allow a smart character to notice how the mechanics work, while Dexterity is used to actually deactivate it. Something like that. You could go further and say that Dexterity is needed for more sensitive tasks, while Strength works for more brute countermeasures like holding a gear back, smashing a rod, or breaking a chain.
Disable Device would represent training in this sort of thing, giving you a flat bonus on whatever ability score you use. You are just outright better than the typical person. Going back to the previous packet, at certain levels you can opt to boost one or more skills to represent that you are getting better at a skill (or increase your skill die if you wanted to keep using that mechanic). From there, you could take a Disarm Magical Device skill trick that lets you disarm magical traps (or even mess with magical constructs).
But ultimately it is one thing to just look at the rules and something else to play, so we will see how it all pans out this weekend when we take a jaunt into the Mud Sorcerer's tomb.