I have to say I am very disappointed with Pathfinders Take on Paladins. You have failed to address some of the the major flaws in the class and instead have opted to add some shiny special abilities and call it good. Not that I don't like shiny new abilities, they are impressive and fun, but I had seriously expected more from you guys.
Problems, in no particular order besides the first:
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MULTIPLE STAT DEPENDANCY: It is nigh impossible to play an effective paladin with anything less than an effective 28 point buy. At anything less than an effective 32 point buy your still better off playing a fighter, barbarian, or cleric. Even at those exalted heights, your probably only going to be "almost as good" as a melee cleric or barbarian.
This has been a problem since (I believe) first addition. Paladins need a grand total of 4 primary stats, more than any other class. Strength and Constitution are both needed to supply the paladin's front-line agenda. Charisma is needed for all of the Paladin's special abilities EXCEPT spell-casting, which requires wisdom to the point where you must have a mod to start getting spells at the proper levels.
What's more, skimping on the remaining two stats hurts the Paladin severely. Skimp on Dexterity and your AC goes down, lowering your ability to tank for the party. Skimp on Intelligence and your already low skill selection becomes even worse, and leads to the "Lawful Stupid" type of paladin. The lack of Intelligence combined with the holy bent of the class has made the Paladin into the Jehovah's Witnesses of DnD (No offense to any JWs out there).
This is crippling at lower levels, where the game constantly demands that every member of the party be fulfilling a role. Assuming a 26 point buy, what is a paladin going to do? He will either have to stat himself like a fighter (giving up a large part of his paladin abilities in the process and not gaining anything in return) or spread his points out, wherein he wont be doing ANYTHING as well as the other classes potentially could. MSD is the most pressing issue facing paladins.
D8 HIT DICE: Is this a typo? Why was this change made? Paladins are a good attack progression melee class. They wear heavy armor. Why are they now getting the same HD as a cleric or druid, without the major perks of a full caster progression? The paladin mount is not THAT good. Doesn't this go against the design template laid out on page 35? What is going on here??
0-SLOT SPELL CASTING: Throw us a bone here. Paladins are already strapped for stats, and now we have to have a higher wisdom than other classes to even cast our spells? Frustrating, particularly when you are unlikely to be able to afford a Periapt of Wisdom on top of new armor, rings of protections, gauntlets of ogre power, con boosers, etc etc etc. Just give us a spell already, we don't mind waiting a while for the next one.
No Detect Evil? The non-caps title indicates I am of two minds about this. On the one hand, Detect Evil is a pain to use, a pain to mediate, and can often wind up turning allies against each other. It has led to the dreaded "Detect/Smite" paladin, which may be the very hight of paladin idiocy. On the other hand its a very flavorful ability, making a paladin very hard to deceive by the forces of evil and offsetting the lack of talent points to devote to sense motive. I could swing either way on this, and if the MSD issue was solved this would likely become a non-issue.
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Thats not to say there is nothing to love about the new paladin. The change from Turn Undead to Channel Positive Energy makes that ability significant again. The new ability to enhance your weapon instead of call a mount answers another significant problem with the classic paladin: Horses cant enter dungeons. I love the new Aura powers, particularly Aura of Justice and Aura of Righteousness. The 20th level capstone ability is a solid reason to stay in the class... if you can get to that point. But these problems are band-aids on the glaring weaknesses of the paladin class. There are some easy fixes that can be made, thankfully.
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SOLUTIONS:
Change paladin spell casting to run on Charisma instead of Wisdom. This fixes two problems with one change, first reducing the number of stats that the paladin relies on to 3 and making the annoying 0-slot spell casting less of a problem, since any paladin worth the name is going to at least have 12 charisma. With the new range of paladin abilities, a paladin will not feel as bad loosing some Dex, Wis, or Int to push up their charisma, and this allows for flexibility and diversity amongst paladins.
I would also like to see paladin skill points rise to 3 or 4. Without Detect Evil, Sense Motive becomes a much more important skill for paladins, and Int is still likely to be the dump stat of choice. Since you are still playing a hybrid caster/melee class you will likely also find yourself wanting both the caster skills (Spellcraft, Knowledge: Religion) as well as Paladin skills (Diplomacy, Sense Motive, Ride) and general skills (Perception, Climb/Jump/Swim, Heal)
Thats all I have for the moment. I will add more as I look through the Alpha more, and as other good fixes are suggested. GO FORTH AND DISCUSS!