Here is my opinion on the alpha rules :
Races :
All the races are stronger, I'm not sure that it was necessary. I like the renaming of the different bonus, and the weapon familiarities. The new rule on favored classes is a real improvment.
Dwarves : they gained little things, only the +2 wisdom is significant ; they are one of the losing races in these rules.
Elves : +2 intelligence and the equivalent of the 3.5 Spell Penetration feat make them really powerful wizards ; I think this is really too much : elves are already a good race.
Gnomes : only a significant +2 charisma, still no love for the gnomes ; the race lacks the faerie aspect they are supposed to have in Golarion.
Half-Elves : +2 to anyone ability, adaptability and the new favored classes rule make them a really strong race, Half-elves rule in Golarion ;)
Half-Orcs : no intelligence penalty is good, +2 wisdom and Orc Ferocity make them more appealing.
Halflings : only a +2 intelligence but they didn't need to be changed a lot.
Humans : +2 to anyone ability and all the good crunch of 3.5 still make them a powerful race.
I don't think it is necessary to give too much to the races : the additionnal +2 bonus are a little bit too much for me (except for the half-elf). The gnome need to be deeply changed, humans, elves, dwarves and halflings are good as they are, half-orcs are fine without the intelligence penalty.
Classes :
First, I want to tell you that the three XP charts (slow, medium, and fast) are an excellent rule !! More feats, why not ? I will talk about the skills later. The unification of BAB and Hit Dice is good but sould be D6 for medium BAB progression and D4 for slow BAB progression. The options for the starting Hps are good ideas to avoid the ON/OFF aspect of first level.
All the classes are stronger but here also, this is not even between them : fighter gain a little, rogue, cleric and wizard gain a lot.
Cleric : not a lot of changes except Domain powers and Orisons. Orisons are ok, I'll talk of Domain power later.
Fighter : still a lot of feats, and now armor specialization. The weapons group are interesting but the class is still the poorest of all.
Rogue : first, sneak attack works against any (almost) foe, why not ? But that's already a big improvement, I'm not sure that the class needed anything else.
The rogue talents are a good idea, but some are more interesting that others : Ledge Walker and Fast Stealth are too specific and should be merged ; what is the need of Finesse Rogue ? Simply give Weapon Finesse to the class at first level. Major Magic should be an Advanced Talent.
Wizard : Cantrips at will, why not. I'll talk of School Powers in the Magic chapter.
All the classes gained, but the ones who gained more were already the more powerful (casters) or the more fun (rogue), I think this is one of the major problems of the alpha rules.
Skills :
The new skills system is right between 3.5 and 4th edition. I don't know what to think about it : I really liked skill points, but it's true that it was too hard for some classes to put points in essential skills, like Spot or Listen.
The new system is fine on this aspect : any class can decide to train in Perception, and there is enough differences between a trained class skill and a trained cross class skill to keep class skill significant. Moreover, the gain of new skills is a good thing. One little thing to do could be to go deeper in the fusion of skills. A little concern is that it is really too good to take a first level of rogue and then change to the class you want to play.
Appraise to identify a magic item is a wonderful idea (but the Identify spell should be removed). I'm not very fond of Sense Motive merge in Deception, but that's not a major thing. Fly is a good idea but it will be weird to see a 1st level character trained in this skill. Linguistics is nice, I like the way you can learn new languages now !!! The merge of Concentration and Spellcraft is excellent to.
Feats & Combat :
Well let's talk of combat first : I'm not sure the new rules fo cover were necessary. I know that the 3.5 rules for this are not really good but the good thing is that they are fast and intuitive, that is not really the case with the new rules.
The CMB is a very good idea (the greatest of the alpha), in itself ; but I have a little concern about how it is used.
All the feats about the combat maneuvers have been standardized, and the way you use Combat Maneuvers too and that's a huge improvement.
My concern is about Disarm : a fighter can't use his Weapon Focus feat, or Weapon Training to resist in a better way to a Disarm attempt against him ??? I think that Disarm shouldn't use the CMB, just like the Feint maneuver and stay like in the 3.5 an opposed attack roll.
Most of the feat changes are good : I like the new Poser Attack. The obligation to use some feats if you have used one of the prerequisite feat the round before is an interesting rule but it needs clearier explanations for some feat trees, like Dodge/Mobility/Spring Attack : does the new rules mean that you can use Spring Attack only one every 3 rounds ??
The new turning rules are not bad but it shouldn't force undeads to flee the cleric, it should just prevent them from approaching you.
Magic :
School & Domain Powers are working in the same way or nearly, that's a nice idea but they are really too strong, or wizard & clerics should have less spells per day.
The correction on spells are not he one I was waiting for : we need rules to avoid the Scry/Buff/Teleport syndrom, and kill all the spells that overpass skills : Commune, Speak with Dead, all the Detect spells are the most obvious. Moreover, Make Whole shouldn't restore magical abilities : characters must be able to lose some magical items from time to time, and sundering them is the easiest way.
The last chapter on Building Encounters and XP is an interesting one.
As a conclusion, he is what I think of the alpha rules : the intentions are really good but too often badly done. Too many times, it ends up with some power creep for the characters or a complexification of rules. Moreover, at the exception of the Combat Maneuver Value, it does solve the problmes of 3.5 edition.
I liked the races and the bonus to ability scores. Less reason to take a +1 ECL template or race IMO.