Removed them today from the back of my case. By gosh does the airflow increase! And the temps have dropped a fair bit too.... From 55/33 to 50/28. Lovely.
Can't believe how toss those fan grilles are that come with cases... They must restrict about 80% of the airflow.... Well they DO restrict about 80% of the airflow, I've felt it myself!
<3 Dremels