Just finished marathoning the rest of the anime series. I didn't watch the OVA yet, but since it appears to be a big shift in tone, I'll leave it for tomorrow.
Quick impressions for episodes 9-24 and the anime in general:
• The first assault on the lab was adapted beautifully. It's pretty much the way I imagined it, and it even matches with my description in the OP. With the atmosphere turning surreal, with the sound becoming muffled, with Okabe viewing things at half speed. Really well done.
• Faris and Luka don't really get enough screen time to make their D-Mail arcs work as well as they did in the VN. In the VN, I was constantly being seduced by Faris, or learning more about Luka's insecurities. Also, we didn't get an anime version of Faris's kickass Rainet match against the Viral Attackers. Disappointed ;_;
• Moeka's beatdown scene. Holy crap! I was afraid they'd censor that scene (by panning the camera or something similar), but are you kidding me? -- Okabe straight up PUNCHES her face in! I don't think that even happened in the VN! Goddamn! The part where Okabe is on top of Moeka was also modified so that instead of silently sobbing, Moeka cries out in despair when she realises FB's betrayal. It was a different approach than the one the VN took, but it also worked quite well, and I'm glad we have these two different takes on the same scene. Moeka's VA was also very good during the entire scene.
• Moeka's murder in the same worldline was changed. Instead of Nae killing her, FB himself did it. I'm guessing they did this for time reasons, but ultimately it changed the meaning of FB's suicide. Instead of it being to protect Nae and Moeka, it ended up being only for Nae. We also didn't see psycho Nae all ;_; Even the scene where she throws Mayuri in front of a train was changed to make it look like she tripped, instead of leaving her intentions ambiguous, like in the VN.
• The anime in general was really well directed. Coming right from the VN, you can clearly see the parts where they purposely didn't stick to the VN's mood because it wouldn't work as well with the flow of the anime. For example, there are a LOT more scenes with no background music in the anime than in the VN. There's also more silent contemplation, as a result of not seeing Okabe's thoughts all the time.
• In conclusion, the anime is a really good adaptation. I can't point out any obvious flaws other than a few scenes that I wish were in or a few others that I would have preferred if they were adapted in a different way (Jellyman Mayuri, c'mon son). I had the story really fresh in my memory, and it was still a great experience. That's a clear indication of how good the anime is.
• The true ending credits scene was left in yeeeesssssss
I hope they can publish the movie over here as well. I'll purchase it right away.