When my sister mentioned that this had been released while describing it as "filler", I was immediately disappointed. "Isn't filler supposed to be exclusive to properties existing in radically different media? Like the manga-anime deal?"
Upon watching with low expectations for the story, I was pleasantly surprised in almost all areas. Rather than simply filling time, a decision that would make no sense in this medium, you seem to have rather used this episode to develop the universe and the characters. This is good. Showing off the new art assets is cool, too.
Revealing more about how the hell things work is always a good thing. The presence of questgivers and associated quest content, the brief depiction of 'hax' in action, automated lockouts for compromised battle grids, Alpha's ability to blast right through said lockouts, and the foreshadowing that is the Shadowguard Beast all effectively flesh out the world where the characters live.
The dialogue is better still than EP3, though there are still a few lines that I think could have been improved. One in particular sticks out in my mind, Kirb's use of "fairly certain" in casual conversation seemed forced. Who chats like that? Usually people either talk casually or use overly big words to enhance the comedy of their speech, and "fairly certain" falls in the decidedly-off middle ground between the two. "Pretty sure" would have probably felt more natural.
Rockoon got a tad more detail to him as well, I like that. An implied past in roleplaying, apparently did his raccoon research, finds his own voices entertaining but tiring on the chords, the works. I found him entertaining but slightly generic in his first few appearances but I think he was better in this one.
Exploration of the main five was also well done. I'm intrigued by the circumstances that GC says keep him from meeting the others, I'm curious as to the nature of Nylocke's falling-out, I'm interested in the real-life meetup plotline and hope it gets a mention in the future.
I do think is episode ended a bit weakly, though I guess I may have been spoiled a bit by the first episode's intense ending clip and all the ones after it have been a tad underwhelming. This one in particular was predicable and a tad slow on the delivery, not unlike the old Road Runner cartoons but without the timeless appeal of watching Wile E. plummet out of sight and crash in a blast of smoke and debris.
The music is starting to repeat more noticeably. Character theme songs are starting to define themselves. This is good.
This may or may not be the best episode yet, but it's definitely right up there. Keep up the good work, and take as long as you need on EP5. Within reason, of course.