What I did enjoy with Brigadoon was how effectively it went into its more serious elements. Marin is portrayed as a believable tragic heroine whose tragic past, current upbringing and connections to the Monomakia regularly put her at odds with classmates and others among the human populace throughout the show. She gets regularly bullied for her social status as an impoverished orphan and this worsens throughout the show as her bond with Melan Blue against the Monomakia threat leads classmates, the police and citizens to lash out at her at points thanks to personal tragedies and thinking she has something to do with the problems humanity is struggling with thanks to Brigadoon. Melan also makes for an interesting character as well as he adapts to living life on Earth and tries to maintain his loyalty and growing bond with Marin as he comes at odds with other Monomakia, a few of which being former comrades he used to coexist with before going rogue.
Brigadoon is also good at keeping you hooked on its plot developments as the merging of Brigadoon and Earth leads events to worsen throughout the show. The series slowly reveals more about the world of Brigadoon, Marin's possible connections to the world and characters taking their own different routes with trying to manage the problems between both worlds. Mood whiplash happens quite frequently throughout the show as Brigadoon juggles between light-hearted moments and shocking plot twists that worsen the situation faced by Marin and other characters. The series isn't afraid to kill off major characters or put said characters in life-threatening situations stemming from the Monomakia threat.
Still though, my praises for Brigadoon's serious elements still suffer from the title's more comical elements. I found the show's attempts at comedy as a breather from the more serious moments to be quite hit or miss as I much rather enjoyed the light-hearted moments of bonding Marin had with other characters over the show's comedic moments. With its comedy, the show quite often gets in the annoying habit of fooling the audience with Marin have a bizarre dream over her thoughts of any serious moments that take place throughout the show, and they are quite often a mood killer following the show's serious moments.
Brigadoon's more serious elements are also not safe from criticism from me. Many of the shows' early episodes tend to follow a "monster of the day" type plot that do nothing to advance the title's plot and I did often find myself getting creeped out with the frequent occasions of seeing Marin and a couple other girls around her age being nude. The final episode of the series was quite a letdown as well, having a good amount of deus ex machina to undo any major character deaths taking place, leaving Marin's connections to Brigadoon unclear and any details concerning the major foes of the series rather vague.
Visually, Brigadoon is rather average as character designs are on the simple side with details and look a bit rough with their lining with the childish-like style to many designs taking away from the seriousness of the series. Scenery is well designed having vast shots and a nice amount of detail applied to them. Animation shortcuts happen rather frequently throughout Brigadoon with speed stripes, still shots and reused frames being the norm with it.
Musical tracks do their part in accompanying the show's calm, comical, serious and dramatic moments. However with exception to the anime's OP musical track "Kaze no Ao, Umi no Midori", the soundtrack to the series isn't too memorable for me.
Overall, I felt Brigadoon's mixture of comical and serious moments in exploring Marin's ordeals with her everyday life and the Monomakia to be quite hit-or-miss for me. While I did enjoy much of the show's serious approach to its story, the comedic moments were too much of a mood killer for me and the final episode felt too convenient and open-ended with how it resolved its major plot elements. I suppose your mileage will vary with how well you warm to the series since it looks like Brigadoon has a cult following among anime fans.
