I never read or played Nobilis 1st or 2nd editions, but Nobilis 3rd edition is excellent. It is not like most RPGs, in a number of ways, but I feel it gives more freedom than the average RPG as well. I have never felt more capable of designing a PC whose concept is whole and compelling than when I used the diceless systems in this book to create sample characters.
Others have said all of the big details better than I have, so I will leave it at this. Buy Nobilis, read it over a few times, give it a chance. You won't regret it.
[5 of 5 Stars!]