I'm intrigued and excited by Paizo's continued evolution of the 3E ruleset with the Pathfinder RPG, as opposed to the revolution in rules represented by 4E. After reviewing the Alpha, I thought I'd post my own suggestions.
1. Point Based Ability Scores and Fixed Hit Points: These should be the default character generation methods, with random ability generation and hit points as options for gamers who prefer this method. Why? For one, you can generate higher level PCs and NPCs faster. Second, it enhances portability of characters between campaigns by establishing a standard - which is why point based ability scores and fixed hit points are used in RPGA's Living Campaigns. Third, I've seen too many 'Randomness is fine - just reroll 1s, 2s, etc' comments - if 1s and 2s aren't acceptable, then the method itself is flawed. Again, lets not eliminate the option of randomness for those that prefer this method, but the inherent balancing and fairness of the fixed system should make it the default method.
2. Multiclassing: I already like what Pathfinder does with Favored Classes. Lets go further. The Unearthed Arcana rules are OGL and have a lot of great ideas for multiclassing - incorporate what works. Magic Rating for non-spell casting characters makes multiclass spellcasting a more attractive option. Fractional BABs and Saves also eliminate the multiclass penalty. Multiclass Feats in the theme of those that the Complete books introduced - that allow certain class levels to stack for specific features (such as Ascetic Hunter) can also enhance the multiclass experience.
3. Arcane Spell Failure: Time to go, completely. ASF is a clumsy mechanic - nothing else in the game relies on percentile rolls in combat. I recommend disallowing arcane casting in armor for anyone who does not have the requisite class feature or feat. Instead of reducing the arcane spell failure chance, the Arcane Armor feats should permit spellcasters to use a class of armor - i.e., Arcane Armor Training (Light) would permit casting in all Light Armor, Arcane Armor Training (Medium) would permit casting in all Medium Armor, etc. Use level and feat prerequisites to ensure these feats are balanced.
4. Saves as Defenses: Saves as Defenses isn't a 4E innovation - this has been around since Unearthed Arcana. I prefer that player spell casters make the roll to see if their spell works, as opposed to the DM making a roll to see if it doesn't. Putting the dice in the hands of the players is almost always a good change. This also speeds up combat - instead of the six Goblins in the Wizard's Fireball burst radius each rolling a save, the Wizard makes one roll, which is compared to each Goblin's Reflex Defense.
5. Class features: Love the Rogue Talents. I'd like to see some of the Shadowdancer prestige class features appear as Rogue Talents. If Rogues are masters of stealth, then Hide in Plain Sight should be a class option. A talent that grants Darkvision should be another.
6. Spells for Rangers, Paladins: I've always liked the Holy Sword spell for Paladins - a great pinnacle spell for the class. Rangers and any other 4 level spell caster need their own pinnacle spell, such as Bane Bow from the Complete Warrior. If Rangers are to remain spell casters, give them worthwhile spells!
Welcome your thoughts, and thanks to Paizo for giving us the opportunity to voice our suggestions!