I kept on seeing commercials for this show on Comcast On Demand, heard the line "girls form band over their love of K-Pop", and thought why not.
FIRST OFF: This is not a K-Pop show, nor does it feature K-Pop specifically. One of the main characters may be Korean and dress in typical cutesy Otaku clothing but that is the end of it. There is also no mention of K-Pop at all in the show or by the characters. Advertisement's should stop mentioning K-Pop with this show immediately, that is false advertisement.
Now that you've dropped the hope of seeing anything K-pop related, this isn't that bad of a show. Keep in mind this is a show catered to young kids - tweens who enjoy musical performances. Think of a mash-up of Zoey 101 & iCarly like characters and situations with sprinkles of Victorious- like stage performances.
First episode was . . . interesting. Compared to other new Nick shows, the pilot wasn't terrible but it didn't wow me. Sun Hi and Caleb seemed like caricatures more than actual people. There was a lot more diversity than I expected coming from a Nick show but as others noted, there is no Asian male characters (of the episodes I've seen so far). It was way more colorful than I expected. It is also a pre-dominantly female cast with one male main character.
After the pilot, we got to see more relatable personalities from the main characters; Corki is straight-laced student who is pressured by her father to perform well in everything academic but finds an outlet with the girls. Sun Hi is an eccentric girl proving to herself and her parents that she isn't a disappointment just because she'd rather pursue the arts than academics. Jodi is a loyal and talented fashionista and dancer that seems to mellow out Sun Hi's loud personality.
Overall, the show isn't that bad compared to other Nick/Disney shows, the music is decent as well. Just don't expect to hear anything other than Pop. The set itself and the characters' clothing might be too colorful for a lot of people but you'll get used to it. The characters outfits are a lot more louder than their actual personalities (excluding Sun Hi), so don't be discouraged at first sight. The situations the girls get into are definitely on the exaggerated, slightly ridiculous side but not as outrageous as other kids shows (Dog with a Blog, etc.) Also, the episodes seem to always end on a cliffhanger (if you can call it that) and end abruptly.
So if you want a realistic show with life-lessons aimed towards kids, this isn't the show for you. Watch Girl Meets World for that! If your kid is bored, likes Pop, and wants to be slightly entertained, this is your show.