The chracaters are boring and cliche. It killed its own potential with the boring fillers and the cheezy romance, bad fanservice and a cannon hentai... Do I need to say more? -_-
Doesn't have hentai.
There is no fanservice.
There weren't any bad fillers, if you actually remember most of it it all served a purpose to the main plot.
People are just mad because the 2 main characters ran off and had some romance time in a forest for a few episodes and the other characters didn't get proper development.
People are also mad because it turned into a ''gay fairy game'' eventually.
To be honest, if you like Kirito and you like the other person he is going to meet, you will love this anime.
If you don't like Kirito then you won't like this anime because this mainly revolves around him and the other characters don't really get any development.
Edit: I'd like to add that there will be a strange relationship halfway through the series between Kirito and his sister.
It ends up all good but allot of people didn't enjoy it.
The action scenes are also pretty good.
Kirito's other half will face an unfortunate event halfway through the series and go from hero to zero for the rest of the SAO story, literally.
Out of all the 13 released volumes after Aincrad there is only 1 volume (Mother's Rosario) and 1 story from the extra volume (Legendary Sword Excaliber) where she still gets to be badass.
