i use the hero i have with a N router in mix mode. im in the same room as the router and i have never had it drop. it MAY drop if you put the phone in sleep mode for a length of time but should lock right in once you power that sucker back on. if it drops just sitting there i would ask you if you have other wireless devices that have the same issue. could be your router's signal is being interfered with other WIFI environments, or , depending on what freq your router operates, cold have other interference (cordless phones, microwave ovens, etc etc...)
