Ditto on the dittos.
And yeah, it's pretty bad. I try to give people a heads up about it, but it really doesn't seem to bother some. I can't tell if that's due to the investment in their purchase and they'll avoid one with it in the future, or if it's a different-strokes thing and the rest are too ..../sensitive (not to be confused with ....-sensitive).
All airholes whistle due to the air rushing in, but when they're smaller it generally happens at a frequency you can't hear. If you decide to have larger holes in your design you can work around it by playing with their shape, like chamfering (google and you'll get the idea) but if you don't... you could still play with getting the airholes chamfered on your own.