Spoiler free review!
This is a really good anime to get into if you have an interest in gaming, especially the MMO genre. Its animation during battles are very impressive, and has a great soundtrack.
However, its downfalls are how we don't see the majority of the "character development". We're told that the characters would know each other for X amount of time, but we only see glimpses in comparison to how long they are in the game for.
"God-mode"-ish type of abilities are left unexplained, just something certain characters have for no reason, it seems. Certain characters show a lot of potential and come off as strong characters, but only to disappoint a bit.
Nonetheless, it's clear the anime has a lot of potential when introduced, just don't have high expectations. It's worth a watch.