I bought this Plantronics headset for my husband to supplement my own&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/PLANTRONICS-DISCOVERY-925/dp/B001S9EYN6/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">PLANTRONICS DISCOVERY 925 </a>&nbsp;when we were taking a trip in two separate cars so we could communicate safely on the road.  He had not previously used a bluetooth device, and I wanted to make sure that he could answer his phone without taking his eyes off the road.  Both of us were using the new iPhone 4.  So how did the Discover 665 compare to the 925?  In general, it worked well, with easy pairing and one-touch answering.  Where it lagged, however, was in audio quality. I could hear him, but he couldn't always hear me, and occasionally his transmission had some vibrato and/or muffling.  While the problem could have been with my 925, I've used it for years without such issues.  He has since used it to answer calls from our land line, and occasionally the sound quality just isn't there.