I just finished the Red-K episode and I really liked it, the series continues to impress.
As I said up-thread this is the "first" use of Martian Manhunter and I still stand by that statement as I meant it in its larger context (the Smallville and 90s JLA live-action versions not fully counting) and it continues to do a good job. Just, DAMMIT! Can we see a half-eaten packet of mini-Oreos in his hand at some point?
The use of Red-K here was interesting, it took the effects, largely, from Smallville where exposure took away Clark's inhibitions and societal politeness and made him an asshole, but one born from his repressed feelings. It basically makes Kryptonians mean drunks. (

) But the exposure to it seemed more born from the comics where is a one-exposure thing, not that they had to be in constant exposure in order to feel the effects like with Green-K. (In Smallville, Clark had to be constant contact with the Red-K to feel its effects, here Kara is exposed to the Red-K (at a good distance no-less) in order to be effected. In the comics Superman only had to be exposed to it for the "random effect/hey we need something silly to happen in this issue because its the Silver Age and the CCA" to take place then that particular piece never harmed him again.)
Interesting that it wasn't a "naturally occurring" version of Kryptonite and was a synthetic one, which would suggest Superman has never been exposed to Red-K and thus, presumably, no other kind of Red-K.
In Smallville usually the after effects of Red-K wouldn't last outside of the episode. Maybe a tiny arc where Clark struggles with Lex, Lana, Chloe or whoever for an episode or two but mostly it was back to life as normal where everyone shrugged off that time when Clark acted like a complete asshole and maxed out his parents's credit cards. Here it looks like Kara's Red-K exposure is going to have some lasting impact, if only for a single episode. But I doubt they'll have her repair her rep with the city and more notably with Jimmy in a single episode.
I still think Benoist does an amazing job in the role and, damn, did she look good as Red-K "civilian" Kara.
Got to admit, the show is good. Like said up thread, it's because the creators behind it aren't shying away from the notion of a positive/upbeat superhero and realizing just because she has near limitless power that doesn't mean there can't be challenges. I've always argued when it came to Supes the more interesting thing is how he as a person deals with things, his regular life and the Superman life, than it is in how he overcomes the physical battles.
Can you even imagine the brooding, dour-faced, scowling Superman from the current crop of movies taking a couple minutes out of his day to stand-up for a kid being bullied and to act like they're best-friends? I loved that bit in Supergirl because it felt like, well, Supergirl to some degree. It also felt like a version of Superman we've not seen in a while, particularly in film.