Note my review is for the CN version which has been running for about a year now.
Characters are good. I won't say that they are particularly outstanding, but they have good art and are well-developed to be above most gacha games. Also, before you ask - yes, there are husbandos in Girls' Frontline.
Now that's a husbando.
Media is amazing. The UI/UX is a bit generic, but it is clean and minimalist, and a huge improvement from Girls' Frontline. The Character Art is great; the Live2D Skins are really high quality.
Monetisation is probably among the best for a gacha game. You get about 57 Pulls / Month as a F2P (excluding Events), which is generally enough to get the one new character launched every month. Gacha is standard - 3% for a 3-Star, and Pity is at 60 for a random 3-Star and 180 for the featured 3-star. You should expect to have about 90+% of the roster within a year.There’s little room to whale, mostly because there are diminishing returns for the amount of money you spend. There’s a Battle Pass (US$10~) and a Monthly Pass (US$5~) that offers 14 Pulls (plus Skin) and 16 Pulls respectively that are worthwhile though.*
Gameplay is surprisingly deep. Stages are randomly generated so you can’t just copy someone else. There’s a lot of strategy involved, meaning you have to use your brain. However, there’s a lot of Quality-of-Life features that let you auto or skip battles you’ve already completed - you can finish your dailies in about 10 minutes. This makes it really suitable as a side game you can finish up quickly if you're busy yet have lots to do when you're bored. There's not that much powercreep (yet) and all characters are viable, though of course some are undoubtedly better than others.