Don't get fooled by the first episode. This show is pretty bad (at least if you expect quality writing out of it).
The main problem for me was the lack of story. They setup a life or death siutation but instead of showing the players coping with it we get a timeskip and a chronological adaptation of the source material (light novels) which means lots of irrelevant side stories. The stakes are mainly ignored and hardly anyone works toward the goal of completing the game (clearing all 100 floors). When the SOA story arc comes to an end it is abrupt and makes no sense at all due plotarmor. The second arc is still airing but luckily it'll be over soon. All changes have been for the worse.
Another issue are the characters; cardboard cutouts and personality changes on demand. Most of the women (or better girls) tend to exist to form a harem for our MC. Speaking of which, this show goes full-shonen as far as his powers go. It is ridiculous what he can pull off (getting his own skills in an mmo, hacking, highest leveled player in the game when all you see is him idlying and helping lowlevel players.. it get's even worse in the second arc).
Given that it is an action show you would at least expect the fights to be good. Unfortunatly these are a letdown. The bossfights usually look rather bad. Not only because of the CGI but the way they animated it. There is hardly a battle choreography and they overuse still frames. You can literally see that the only things animated are the flashing lights which are supposed to represent sword strikes.
Add to this the ever increasing fan-service, silly dialogue, unbelievable romance and countless things that make no sense.

Due to reasons I cannot understand this show is popular and sells really well so a second season could happen.