I think it depends on the campaign world, but in general classes are a good thing. Look around, you have poor people, middle class, upper class, and stinking rich people. I think classes are generally a good thing for people to include...
OH, you mean charecter classes. Yes, I think they should be in DnD, since its part of what makes DnD... DnD. I've never felt confined by 3rd edition. 3rd edition is not about whatn you cant do, but what happens when you try. Want to be a mage who wears full plate, go for it. Granted, you're spells will fail often, but you can do it in 3rd edition, something undoable in 2nd.