Well, think of it this way. Asuna is one of the main attractives to this show, for many different reasons; ALO just completely destroys the character in favour of turning it into a lame plot device to keep the cow milking. The whole premise of how it got to where it got, as well as the whole imouto deal just irks me to no end, it's like it wasn't meant to be there to begin with (which it really wasn't).
IMHO, SAO would have been a much better show had they only focused on the SAO part, giving it an actual ending there and that's it. I'd also have entirely scrapped side characters like silica and liz, in favour of having a better development of the friendship with Klein, which is supposed to be Kirito's best friend, but it's like we only see him when the author goes like "hey, we need some character development for kirito and we need to make the story move, get Klein in there so we can do something," which was a pretty shallow way to abuse supposed friendship, since there wasn't much interaction between the two.
Overall the idea behind the SAO arc was nifty, but it was mostly badly employed, so I have mixed feelings at best for the first 14 episodes.
Past that I just see it as milking the franchise, since the author originally intended only for the first novel to exist, but then it kind of went on without polishing some stuff up. It was supposed to be online only, but then, what with the success it was gaining and all, it just went on for more than it should have. Furthermore the side stories, which take up like almost half a dozen episodes, are just part of the tie-in second novel, which again was done later. The first novel already hinted at character and events which are expanded upon there, but it's stuff that could have just been left untold or explained with quicker flashbacks, rather than dedicating entire episodes to them.
So yeah, by now I'll just finish it, but you can see how one would generally say it got worse. And imho its flaws didn't make it half the show it could have been in its first half either.