The lack of classes and birthsigns bothers me because it tells me nothing of my character.
In Morrowind, I could choose a Monk character and go with the route of acrobatics, speechcraft, hand to hand and restoration. I was playing a role. I KNEW from the start what my character is good at. I KNEW what he will do in this land, how will he react, fight and explore. The birthsign gave me an extra power, an extra option. As a Monk, I'm bad at fighting, so why not choose Warrior sign? Wanna be more harder to hit, since I'm a Shaolin Monk? Ok, I will pick Thief which gives me 10 points in Sanctuary. This things were important because it made me choose a ROLE (in a role playing game!!) and it made each character unique and different from other characters.
In Skyrim, from the beginning of the game, you are a jack of all trades. You can cast any spell you like without failing. You may wield any weapon, carry any armor, make any potion, pickpocket every person. There is just no point of "restricting yourself" when you are good at everything. Why create new characters when with one guy you can be everyone and everything?
In theory I can make a jack of all trades with 100 in each skill, but it will be a lot less effective as a jack of al trades then a similar person in previous games thanks to the perks and the way they provide bonuses to your character. What I end up with is a more specialized and unique character then I had in Oblivion or Morrowind. My Assassin is good at sneaking, stealing and killing, however dress him up in heavy armor and give him atwo handed axe against an elder dragon and he will be struggling as he lacks the perks to make both heavy and two handed really useful. From the start the character generation isn't limited to this or that class, but to your imagination of your class. I play a nightblade type of assassin, he sneaks around, using Blade of Woe and some magic to help him get away from danger and control triky situations. My assassin in Morrowind and in Oblivin that also had the same starting point as I have today as a nightblade did this. The difference on my nightblade in Morrowind or Oblivion was that at high level they were jacks of all trades, it was not possible to avoid that from happening. On high level in Skyrim my nightblade is still an assassin, sure I can throw other spells, but I'm not really any useful with them. I miss the perks to make Destruction really effective, I miss the perks to make conjuration really powerful. I can heal myself, but I don't have any perks that will make my healing really good. So at level 81 I will have 100 in all skills, and he will still be an assassin. He can choose to wield a two handed axe and heavy armor, but without perks to back them up he is a lot less useful with these then a pure warrior would be. And here you have the biggest difference on previous TES games and Skyrim, while you did become as powerful as others in previous game by getting skill to 100, you will nt be able to achieve the same in Skyrim. So what starts as something that seems to end up as a jack of all trades will end up as something more unique at end levels then in previous games.