Podcast 43 from TESOTR is probably the single best source for insight in what the classes really are with regard to limits and customisation. It's only based on an alpha preview from October but it still sheds a lot of light on the topic.
Download podcast 43, skip the first 10 minutes of yapping and you have around one hour of quality information ahead of you. The last hour is mostly silly and not very informative.
Basically each class will gain a number of unique abilities/attacks as they level up but any weapon, armour, sneaking and related perks seem to be open to all classes. I'm not sure if there are class specific perks.
And I find it funny you talk about classes in TES. I always viewed it as a classless game. Sure, there are premade sets of starting bonuses for your character which you may use, but you can combine bonuses any way you want. There are no classes in the traditional sense of unique abilities and limitations.
Edit:
Oh, I just realised I already posted this link in the same thread a few days ago. Well there you go again. Get educated!
