Yes, I have bought one. Gasp!
I wanted a 6x6x6 cube to go with my V-cube7, Dazzler and Illusion. I decided at the last minute to get a 6x6x6 flag cube instead of the Vcube6, for the sake of a change and trying out something new. I must admit, I did have simular thought to some of you on this thread. I was thinking that maybe V-cube were going round in circles until they got round to offering something new like a Vcube8 for instance. Or maybe it was an angle for marketing. But I had also read on their solutions page that the flg cubes were actually more difficult than they looked. So I ordered one with French flags - I have French nationality.
I was thinking all the time that with the same algorithms I use for the Vcube7 and my 5x5x5 Eastsheen it should be easy. I was ever so wrong.
I discovered that the algorithms I'd trusted to all along for cubes where a whole side is the same colour are not so trustworthy when there is more than one colour to a side. And then once you think you've got it right at long last, you realize that the center part of one of your flags is pointing the wrong way, and you have to undo part of you achievement to put it right. (Or maybe I'm not such an experienced cuber, whatever.)
I realized it was a much more difficult challenge than the other Vcubes I mentioned above. Then when I only had the final side to solve, I had parity problems to get through too. This is all made more confusing by the fact that there are only three colours and it's very difficult to tell which bits are the right way up until you try placing them. You find yourself learning new reflexes very quickly.
Believe me, Vcube aren't just stalling or marketing when they offer these Vcube flag cubes. Get one and try it out. You'll see what I mean.
I don't know about the 7x7x7 flag cubes, but I've read about people having as many difficulties as me to solve them.
You want a new challenge? Get a flag cube! (Will there be a Union Jack?)
PS: I did get there in the end. Vive la France!