new player, I have a question

well, I'd like to know the main differences between the current L2 and chronicles like Interlude. that's the last one I played for long time and according to what I've been reading, there's a world of difference now :\ many things that are not used anymore and other that have been added. So I wannat know the MAIN differences which make the game a different experience. I know of the vitality system which increases the EXP rate for a while, but, besides I've been reading, I think I don't realise the significance of the changes. For example, is that "Path to awakening" something mandatory or it's a help for newbies? Could some experienced player make a summary of differences between now and before?

Thank you a lot.