For me, the sound and tactile feedback of the blue cherries has the same satisfaction as chewing on ice for some odd reason. I think my brain would tune it out as background noise before I get tired of it.
I like chewing on ice...
For me the cherries werent chunky enough... i had to go back to the M to be satisfied. The M's chunka-chunka makes me thing of industrial machinery (and hence a sense of production and productivity I guess). Steam locomotives, factories, mills... etc.
It also helps tune out background noise as pmyshkin says. A kind of white noise that helps you focus, and the more you type and produce, the more steady the noise is, and so you produce even more - there's a "virtuous circle" of positive feedback you can get on to.
When the noise stops I actually miss it

I'm currently considering the Das III, as I love the clicking action, but I'm afraid I won't like it for extended periods of time.
I think the trick is to find a noise that you like. Not all noises are the same, obviously, and your personal taste matters a lot. For instance, I didnt like the white alps noise after a while (too high pitched, and the attack/decay wave was too abrupt, I thought). I like the lower-toned, deeper chunka's of the M. (Made even deeper on my board with a light spot of silicon grease on the springs).
What that means is, while you can get a rough idea of what you might like, ultimately there's really no substitute for acquiring each board you're interested in and trying it out in person. "Its a process". Nothing like a test drive. You can always re-sell the ones you dont want.