One major change I've noticed from D&D is the demand for skill points. Most players when creating new characters (after that nasty business with the werejackals and the sacrificial pit) are putting their second highest roll into Intelligence.
This is a very very good thing IMO.
The Weapon Specialization feat increases both the damage and armor piercing of the weapon by 2. Ditto Greater Weapon Specialization.
1d12 hit points per level instead of 1d10. Straight battlefield training sacrifices your versatility in life (skill points) but leaves you tougher.
I don't know about adding AP to weapon spec. It seems to me that AP is already very closely balanced against DR, with the right weapon choice and a decent Str you should be able to pierce anything but the heaviest armor already. It almost seems powerful enough to be worth a feat in itself, imagine somebody walking around with a greatsword with an AP of 11! That should be reserved for something like a poleaxe.
As for the d12 hit die, I also think that is a mistake. A soldier's advantage is his feats, he can afford to buy toughness which is statistically the same thing.
6+Int skill points per level. [6+Int]*4 at first level.
I have considered this myself, in fact I let a player make a test character who was a borderer with 6 skill points. He also gave himself a 18 Int and by the time he was done he had skills comming out of his ears on top of being an effective fighter. I am not sure if it was the 6 points per level or the 18 Int but he told me afterward that even he felt he had too many skills. I think this needs more playtest but I am currently leaning towards keeping him at 4 points per level based on that test character.
Nomads may take Weapon Specialization as a feat at 7th level or higher, but only with a regionally appropriate weapon and if they meet all other requirements.
I agree with BhilJhoanz that wep spec should be left as a soldier-only bennie. What I have decided to do is change the Born to the Saddle ability so that with a little leg work a Nomad will be able to find a superior horse (more HD, better stats, max HP, etc) for himself. I think that that should just about make the class equal.
What tweaks are you using, if any?
The Noble is the class I feel needs the most tweaking. Keep in mind that I think that this is the best Noble class I have ever seen. Powerful in social situations without being unbetable and still able to pull its own weight in the dungeon. I just feel it could use a little help.
1) A good parry bonus (instead of a medium bonus). I think this makes sense given the noble's flavor as a "civilized" warrior, it has a nice symmetry with the Bbn who has a good dodge and poor parry, and it is balanced mechanically because for most nobles Str will be a third or fourth level stat. It also makes Noble a good multiclass choice for Soldier which makes sense for all those knights out there.
2) A Social Ability at 1st level. Three levels is too long to wait to recieve what is, IMHO, you class definning feature.
3) Rally is moved from level 16 down to level 8. At level 16 the range of rally doubles to 60' and the bonus doubles to +4. 16 Levels is just way too long to wait to be able to do the "To me men! Gather round me!" stunt. An 8th levle Noble should defenaetly be capable of that.
But honestly, I think all the classes are prety well balanced against each other. Yeah the Bbn is great, but once people get over it I think they will see each class has great potential so long as you play to its strengths.
Hope that helps.