I always thought that I am... was over hyped until I actually bought the cd and listened to it all the way through. I think it deserves to be considered one of her best works. I think it is filled with inspiration and atmosphere and really has some unique sounds going on. It also stands as a strong example of what Ayu is capable of when she applies herself. This may be an unpopular opinion but I actually really like the versions of Daybreak and Endless Sorrow that were used on the album. I also like the regular version of Endless Sorrow and the HALs mix of Daybreak especially, they can easily be obtained by buying the singles anyway.
For me, the most overrated Ayu album is (Miss)understood. I do still love and enjoy that album though. Alterna will always be a top favorite.
I would say that GUILTY is her most underrated album. That album was so powerful to me. Her best vocal performance as well. The whole 10th anniversary era felt like Ayu was really on top of her game.