It's Ami time! The second(?) Sailor Senshi - Sailor Mercury - is finally introduced, ending the weird period filler focusing on Usagi's friends.
The episode starts off with some info dumping from Luna, who put it off until a major plot episode for some reason. In fact, you'll find this an annoying habit of the show; you can immediately tell if an episode is a major plot step because the cats suddenly started info dumping or they fight the Seasonal Villain directly.
In this case, you can tell Ami is a new major plot character as they have Usagi and Luna go to her, rather than have Ami come to Usagi, which is a particularly strong sign.
Outside of introducing Mercury, this episode is structured and plays out like a typical episode. The villain of the week is preying on overstudying students, steals their energy, but now Usagi and Ami team up to kill it. Ami has her own attack - which obviously sucks compared to Usagi's awesome attack. Mamoru shows up to insult Usagi again.
I do think the evil floppy disc is a bit of a silly plot device though. It speaks evil messages to you in an evil voice! Usagi also uses her disguise pen again, which makes me look quite like the fool for insisting she never does, but I promise you it's overused early on. She's also surprisingly specific about what she wants to transform into - not just a doctor, but a university doctor?
The animation is very solid this episode, too. It's really funny when they run away from Mamoru after he catches Luna talking, and the scene immediately after is the famous joke about computers that you've probably seen. I also LOVE Ami's transformation here; whilst the best transformation animation is their second stage/Usagi's third stage one, this is definitely one of the best runner ups.
Overall I give this episode a 4/5. It's a solid plot episode, but it would also be an incredibly solid filler episode.