Scores: Story 3/10, Characters 5/10, Visuals 4/10, Audio 6/10, Enjoyment 6.5/10
TL;DR: this show is a better ecchi in Japanese, but a better meme in English. I wouldn't recommend season one as it has less screen-time of the good characters.
Infinite Stratos and Infinite Stratos 2 were not just two of my first harem anime, but two of my first anime in general, with my initial viewing being in the summer of 2016. I watched it in dub on a friend's recommendation, and gave it an averaged score of 7.6/10 (including an 8/10 for character). How naive and young I was.
This show has a remarkably thin premise: a world where mech-suit units are at the heart of military combat, and only women can pilot them, bar one. The younger brother of a famed pilot and instructor: Ichika Orimura. A high school student sent off to a world-class academy for future pilots, which has only female students as per the premise.
The Infinite Stratos/2 viewing experience isn't terrible- it hasn't aged very well, nor am I enough of a teenager to fully savor this any more, but it's propped up by having a few fairly likeable characters. That said, most of the characters are terrible. Subjectively speaking, the good characters are Tatenashi Sarashiki, Chifuyu Orimura, Charlotte Dunois, and Laura Bodewig. Tatenashi solo carries this show from a 3/10 to a 5/10 character score, while the unmentioned characters range from forgettable to unbearable.
Regarding visuals, I grant the show a 4/10 for being below average, but completely watchable. The CGI of the mech-suits isn't the finest, but it is functional. The characters are quite enjoyable to look at, facial expressions and animations are pretty much on-par for a modern 2010s anime, but the backgrounds are uninspired.
After listening to the soundtrack albums for both seasons and the OPs/EDs, I find the opening and ending themes to be a tad generic but still cromulent. The soundtrack is fairly utilitarian, but there were some memorable tracks which was a nice surprise.
Voice acting. After re-watching both the sub and dub, I'd say the English VA is a winner thanks to foreign accents being used for the cosmopolitan cast of characters; it makes for an amusing watch. Except for the Japanese characters, who have terrible American accents. Laura and Charlotte are awesome in English, but Tatenashi and Houki are significantly better in Japanese- their English voices are downright awful, to the point where Houki and Cecilia are unlikable in English.
In summary, Infinite Stratos 2 is a short series, which I'd say it's worth a watch for a slice of early '10s trashy harem goodness, but Season 1 is well and truly not worth watching.