I finished Breaking Dawn today and it was one of the best books I've ever read (a fairly strong statement from me as I read a lot). It jumped very high on the list of my favourite books (Lord of the Rings is my absolute favourite of all time but I can imagine the Twilight series right after it). I couldn't put the book down and my home :P
Anyway, there was so much happening and lots of vampire stuff was going on (I'm facinated by vampires, one reason why I originally decided to read Twilight). It was well structured, there were so many unexpected twists in the plot (the plot was complicated enough to keep the story interesting but it never became completely incomprehensible) and many new interesting characters were introduced. I literally got goosebumps and times and it made me laugh out loud (I think it's amazing how a writer can achieve that level of involvement from a reader). I was empathizing with the characters and lived in their world.
It feels good to finally know the complete story about Bella and Edward and I can make comparisons between all the books. This would be my order of preference starting with my favourite:
Breaking Dawn - for reasons mentionned above, emotionally strong so it made you really feel something
Twilight - the first book of the series is always good and fresh, interesting introduction to the supernatural world, good structure, makes you thirsty for more.
Eclipse - too much focus on Jacob/Bella relationship but the ending is thrilling.
New Moon - started of far too slowly and not that much happened over all, it did speed up towards the end though, for some reason I found the storyline slightly confusing.
And for those people who have not read the series yet, I strongly recommend it :)