By no means a great anime, SAO epitomises the shonen genre, complete with symptomatic shortages: a story that doesn't really take off, let alone do justice to its premise; art of uneven quality (a few great backgrounds, decent characters, an almost editorial contempt for creature design and execution) and a competent, yet forgettable soundtrack.
In the meantime it succeeds at developing a mainstream experience, sacrificing to the conventions of the genre without altogether turning into a bland, distasteful mess. So I'm happy to say that I waited for (almost) each episode with some anticipation, and enjoyed them (almost) to the last.
By mainstream, I mean that, it doesn't draw on anything extreme. For example it is neither gore nor ecchi, nor outrageously caricatural in any way. So, while this piece doesn't amaze, I have to say that it's pretty difficult to work with the mass of cliches that lie at the core of this thing, and get something good out of it. The downside is that the result strikes me as somewhat immature; the good side, however, is that had I kids I'd rather have them watch SAO than... the hell-of-a-lot-of-other-stuff.