First off, I will say that I am a SONE and I do prefer their original "cutesy" concept.
When it comes to "I got a Boy" I have a lot of mixed feelings. At first listening, like many, I also felt that this song was a hot mess. Not only that, I felt like SM was trying hard to make up for some of the critical success that YG has had over them throughout this past year by trying to give SNSD an "edgy" feel similar to that of 2NE1. This is like trying to fit a square peg into a circular hole. It just doesn't work out. Between their rapping and more powerful dancing SNSD are still doing their usual aegyo. It's a little awkward and makes the concept seem even more forced.
There is a reason why their teaser song,"Dancing Queen", was so popular across all boards. It's the sort of song that SNSD does best and fans have come to not only expect, but love. Not to mention, it was produced around one of the strongest points of their careers. I'm not saying that they shouldn't branch out and try new things as they grow older, but they should also not bite the hand that feeds them. Their last Korean single, "The Boys", didn't do as well as past singles, so I would have thought that they would go with something a little safer this time around.
I can sort of understand why SM tried to make a mash-up of songs work for SNSD, though. They did this with SHINee's "Sherlock" and had great success with it. The problem is, "Sherlock" only mashed up two songs while "I Got A Boy" took on what? Four? Five songs? There is so much going on that it just ends up seeming more like a cluster ******** of sounds than an actual well polished song produced by a big record label.
On a positive note, I will say that the music's transitions did seem to have some sense to them after I listened to the song with English subtitles . Which, helped me to like the song more. I have gotten it stuck in my head, but it's mostly the "I've got a boy, handsome~" chorus. The music video is also gorgeous and you can tell that the girls worked very, very hard on the song's accompanying dance.
I do think that the song would have been much more popular if after the beginning rap was over SM would have kept the tempo of the following music throughout the song, added in the chorus without changing to the tempo very much, and maybe kept in Taeyeon and Tiffany's solos, slowing down the song just a little at that point.
Overall, I think that the song would have been fantastic if SM hadn't tried to mold SNSD into something that they aren't. Although, credit should be given to SNSD for being confident enough to try out something completely foreign to them.
These are all of my personal opinions and I respect everyone's as well.