@tovi and ?
How about a comprimise, why not make the off-style skills cost more points? Say you choose warrior at beginning then thievery would cost two points each and magic three or such or just two whatever... that way you're encouraged to stay in character but not restricted. Skill point system would have to be altered along with this though soemwhat
I'm saying it's perfect the way it is.
And there are differences between classes. Just ask raze. A warrior does more damage per strength point, and a wizard has more mana per int. I'm not exactly sure on how it goes, but Raze made a really long post about it once. That's difference enough.
The point of the game is that you could start off with a warrior, but then you find that you prefer magic and summoning, and end up with a summoner-mage. "Create your own destiny", it actually says it under the title.