Nothing against her, I'm just so used to seeing Aly as Willow that I can't imagine anyone else, especially as she's my favourite character.

Also nothing against Riff Regan, her acting was okay, when I saw the unaired pilot, however I got the impression she just misunderstood the character of Willow. She was...too depressing, while Alyson Hanningan brought this character to life. Seeing some comments on youtube about Riff was lets say out of line, since it really does not matter if she's slim or not. It's just all about the fact she didn't feel the character of Willow the way she should feel it. Joss made the best decision with replacing Riff with Aly, coz Aly was the PERFECT one for the role. She did not really care when Cordelia was commenting on her outfit, because she already had her own opinion on the kind of person Cordelia was, while Willow played by Riff seemed to be really weak and so sad hearing a bad word from someone like Cordy. Also Aly's Willow is so funny, and cool while Riff's lacks of it.