I have a similar mouse with these "dirt catcher" holes (Honeycomb design), it's generally the same as with other equipment:
If you take the time and effort, the equipment stays clean, or have you never cleaned under the caps of your keyboard?
You blow through the case once or twice and it's clean, I don't see a problem there if you keep your workplace reasonably clean. Be glad that brands are trying things out, otherwise we wouldn't be where we are today :) I think the price/performance ratio of this mouse, at least according to the factsheet, seems to be top.
I am definitely curious to see how this new player can position itself in the market :D
