I like class based roleplaying games. I also like skill based roleplaying games. What I don't like is when you try to mix them. Take your pick but choose only one when creating a system please. Why do I say something like this? In D&D if I play a thief and someone else plays a fighter and we are the same level I should be able to hide better, end of story. The thief class is sneaky but in a system that has both classes and skills such as D&D 3.5 you could end up with a fighter out hiding your guy if you did not put any point into hide. This is not how the system should work. Closer to home my cleric had no points in knowledge[religion] till 3rd level while the sorcerer maxed it. This meant that my character, a person who literally talks to his god on a daily basis could not even by the rules attempt a roll to identify a holy symbol of his own religion!
This frankenstein of a circumstance came from trying to bolt on a skill system to a class system. What a class system is good at is quick and broad characterization, the Magic User knows arcane secrets, the Fighter is a master of battle, and the Cleric is a religious type. These are very broad stokes in which to make your character yours. This type of system defines what you can do, not what you can't and in doing so even though the options are few the possibilities are great.
A skill system is the exact opposite of this. By choosing your skills you define what you can't do. If you don't have the ride skill you can't ride a horse while the class system doesn't tell you one way or the other. Some people over time have suggested that you could combine class and skill by doing stuff like changing skills to mean your extra good at it instead of just being a binary where not having it means not doing it. This Wont Work. Or more specifically you could make the system but the players will still play it as if not having the skill meant not being able to do it. With all this though a skill system is not bad. Because of how you create such a system its not just having 3 skills and putting points into a single one every time which would be like a class system but instead you have many options all of which do things worth having. A skill system does not restrict creativeness by restricting options, it creates opportunities for it. A party comes to a deep underground chasm that is not all that wide. In a class system your players just jump over it, this is very straight forward but what about in a skill based system where no one in the group has the jump skill? Well what about using a rope to bridge the gap, after all that one guy took the rope use skill.
Wrapping up I will say once again both systems are quite all right on their own. Combining them though is futility if you are trying to keep both systems intact. They are opposites and they do not attract people. A cleric of Pelor who can't even recognize his own religions symbol when played by the book is a broken mess. Both systems define who the character is but by using opposing systems. Skill systems let you create your character after play, a class system lets you create your character before play. The 3rd/3.5 Edition of D&D is the closest to combining the two systems out there and no I don't mean the actual skill system, I mean the basically free multiclassing options which is taking classes and making them the skills in a skill system. There may be a perfect combination out there but unless you already saw the fact that multiclassing was a skill system I highly doubt you will find the balance point.