When it comes to dancing, I can't say I'm the one to talk but I do know how to dance, though...Anyway, their dance is so easy to catch on. As much as I like the song as a whole, I love the dance too. Like I said, it's easy to cover and also the choreographer was inspired when he made the moves and the connections between them, how they are all put into the light, be it with a harder or easier move. It's awesome.
About the melody itself, well that's something I'm good at. Sincerely, yes, it's catchy and has an epic sound, their voices go well on it and it's a good song. But, some of them don't get the chance to show us their real vocal skills. Also, while dancing I have the impression they lose their air often, though it's not that obvious. Of course, dancing and singing is hard, mostly the chorus (usually that's hard because everyone has to dance on it but sometimes not all of them sing it too; I'm generally speaking) and they try not to show their emotions or something and just smile and also use their visuals but still...I'm a composer, I can't let it off lol.
The MV, is good...Even though I think they could have used some other idea for it, they did use the songs as a source for the plot so it's alright. I don't have many things to say except the fact that...I swear some of the rooms have been used for FT Islands' I Wish music video. If you looks closer at 1:17 you'll understand my point. Oh and, surprisingly, I like the girl from the video. She has good expressions and really amuses me.