I think the reason I would have been disappointed also is because I see that everyday in my neighborhood. I think if you are set out to see something that you are under the impression is a mural for John Lennon and you end up seeing that, you would more than likely be disappointed.
I saw this a few years ago, also learned about it from a travel brochure.
It wasn't too different then, my memory is that it wasn't quite so grafitti-ized, and that there may even have been a pic of John drawn on there, or perhaps the word "Imagine" or something.
Saw it, crossed it off my list, and moved on. To be honest, and don't get me wrong please, I am a FAN, I wasn't even that moved by the Lennon thingy in Central Park.
So I guess if the boys touched it, or lived there, or walked the streets, I'm impressed. Like having a beer at Ye Cracke in Liverpool, that was surreal. Otherwise, it's not the same for me.
But I like the sentiment!