From the publisher (Erisian Entertainment):
The d10 System based on five simple ideas.
1) Everything on your character sheet should have a point and purpose.
Your attributes, your skills, and your special abilities should have some significant meaning during the course of play. More importantly, they should have a direct affect on your character during play. While many of these rules are well-intentioned, they often have the affect of making certain things irrelevant to players. (Does anyone else remember back when the most bonus hit points you could earn from attributes was +2 unless you were a warrior making Constitution scores above a certain point a complete waste of a good dice roll?)
In the d10 system, every aspect of your character is related to his or her attributes and skills. You do not arbitrarily receive more or less hit points simply because of your chosen profession. Your health is based directly on your Constitution score. So a physically fit mage can have more physical "hit points" than a less healthy fighter no matter how the players roll their dice.
2) You shouldn't have to waste your time reaching level 5 just because you want the ability you gain at level 7.
We've all played level based systems in the past and taken a level only because we wanted the cool abilities available at higher levels. While character levels might make sense in theory, in practice, they often serve to limit a player's interest in the game.
In the d10 System, character's advance by earning points that are spent to improve skills and attributes. This means that you only improve those things you wish to improve. Your character becomes exactly what you have envisioned without a page and a half of extraneous abilities you picked up along the way.
3) Players like to be in control of their characters.
Nothing annoys players more than things that affect the character without any player input whatsoever. It's not a big deal to have a character die because an enemy mage threw a fireball at you... unless you don't get to roll a save against the attack.
The d10 System eliminates these joy kills by putting players in control of offense & defense, action & inaction, success & failure. Your dodge is not merely a modifier to the attackers target number to hit your character. Improving a skill is not merely adding 1 to a dice roll. And you cannot improve a skill to the point where failure isn't possible.
4) Every roll should mean something.
In many games, dice rolls are either success or failure with nothing in between. Other games try to curb this tendency by allowing you to knock on out of the park once in a while with a critical hit... almost always balanced by a critical fumble which invariably means that you either dropped your weapon or your bowstring snapped.
In the d10 System, you roll a number of dice, determined by your skill or attribute, against a target number. Each success means something. It means more damage in combat. It means the repair you just made lasts a little longer. It means the character you just performed first aid on heals more damage.
5) Target Numbers and modifiers need to make sense.
Why does my target number increase because I am less skilled? Is the task mysteriously more difficult because I'm standing there? Does the lock become harder to pick because I do not have superior lock picks? Is the sword more difficult to swing because I'm not trained in its use?
No... Picking a lock has a difficulty based on the number of tumblers it has and how delicate they are. My lack of proper tools and training might make me less able to accomplish the task, but they do not make the task intrinsically more difficult. The sword is not heavier because I am untrained. It is not less arrow dynamic. My opponent is not magically more agile. I am less able to hit him or her because I lack the ability.
In the d10 System, situational modifiers affect the number of dice you roll unless the situation makes the task intrinsically more difficult. Shooting someone requires a set target number. If I choose to aim my weapon, they do not stop moving to make it less difficult for me to hit them. The target number remains unchanged. I, however, receive extra dice to roll in the hopes that I will achieve more successes. If I'm shooting them through a bank of heavy smoke, my skill does not diminish, the task has become more difficult.
This differentiation allows for a more realistic modification to ability tests without slowing down game play.