On my end, I'm one of the people who hated it. For one, and there's no way to say this without sounding like a bit of a tool, I find the way gender roles are portrayed in this and other anime like it extremely annoying. When women hit or abuse men it's used for comedy, which really reflects some hatred toward both genders. In this case it happens a few times in the relationship between Kirito and Asuna, but in fairness it's not all that common. It's more extreme about sexualizing its female characters and marginalizing their roles though, with a massive absence of anything equivalent from the guys, even for a shounen, sorry ladies. It gets to the point of being really creepy. Again, in fairness, it's deliberately creepy, but that doesn't make it any less unpleasant to watch. In a more thoughtful show some of that sort of thing might be alright if it were handled respectfully, but in this one it really just makes it a bit more painful to get through. Alternatively these aspects probably provide some fetish appeal, if you're into that, I suppose.
Obviously that sort of thing isn't the only issue I have with it. It's pretty weak in terms of characters and story as well. The root of the problem is that SAO is pretty purely about wish fulfillment so the protagonist is inexplicably great at everything, which is just painfully simplistic and unrealistic, and when combined with his being a bit of a dick makes him really unlikable. Meanwhile the female lead is a similarly idealized fantasy love interest who instantly falls in love with the lead. Which is a problem in and of itself. The romance is a huge, important part of the story, but it's really badly paced, with the two falling ridiculously in love pretty much as soon as they start seeing each other regularly. It really stops being about anything else once they do, too, and since the romance is so weak its domination of the story really drains the show of any entertainment value. It also has a problem of using a few pretty ridiculous scenarios to make the main characters succeed. It really comes to a point where the climax of each half of the story gets resolved with a Deus ex Machina.
There are a few good points, though. Before the romance takes over the story it's a bit more interesting. It gets a bit of mileage out of the premise by exploring the likely results of people being stuck in an MMO, and looks at a few minor characters who, while not particularly likable or interesting, are at least more so than the leads. The production values are also quite high and the fight scenes are good enough.
Basically if you hate anime like Fairy Tail, Naruto, To Love-Ru, etc. You'll probably hate this even more. But if you're into a wish fulfillment scenario like this one offers and want to see a girl showing a lot skin and getting sexually harassed then this will definitely scratch that itch. It'll be even better if you'd like to imagine yourself getting slapped around by your girlfriend a bit on your epic adventure.
