Comfort:OK. Leather ear pads and foam could be softer. Not nearly as comfortable as Bose OE's for example. You can bend/form the mic boom to fit your face. Just barely enough length to fit over my head; could actually use another 1/2 inch extension on both sides.Voice:Great. Good noise canceling microphone. Auto-answer sensor works well; it somehow "knows" when you put it on your head and will automatically answer an incoming Lync call.Music:Don't expect to be wow'ed by it's range. Frequency response on the upper high and bottom low end is lacking a great deal. I thought it had some sort of auto-equalization to adapt itself to music vs. voice.. but maybe this isn't working. For example, a pair of 25 year old Radio Shack "Pro 25" OE headphones are much better sounding at full spectrum.Overall, good for what you probably bought it for. Just don't expect too much out of the earphone fidelity on full-spectrum audio.Outstanding piece of hardware for our VOIP phone system. It doesn't become entangled in women's hair (as happened with a cheaper headset from another vendor). It is lightweight and comfortable. Packs easily in a laptop bag with or without the carrying pouch. Sound quality is superb when speaking and listening. Users love it because they can listen to stereo music when not answering a phone call.Note that the Blackwire 500 series has 4 variants: C510, C510-M, C520, C520-MC510 is monaural (has only 1 earpiece to which the microphone boom is attached). C520 is stereo. Both are built for UC applications and softphones from Avaya, Cisco, and more.C510-M is monaural (has only 1 earpiece to which the microphone boom is attached). C520-M is stereo. Both are certified for Microsft Skype for Business and Optimized for Microsoft Lync.If any doubts, Plantronics has a helpful site and my calls to their sales team have always been met with cheerful and helpful advice.I was concerned that since this brand was acquired by another company they would not support it properly. I was anxious for no reason since I frequently receive updates to keep my headphones working well. I also enjoy the quality that I paid for and the comfort of the headset. I am happy with my purchase.The Cord tends to tangle often while in use, which sometimes impacts voice and sound quality as it twists. Very good for the price though... just more of a warning for those who use daily.When your 3.5mm jack starts acting up (thank you Dell), this is a great alternative using a USB jack which I am told bypasses the Dell settings and is actually better in terms of sound settings. Lightweight, in line volume and mute controls, reasonably comfortable. Only gripe is the headband doesn't go larger for my big head but I can put it towards the back of my head and it worksI use Microsoft Lync for all my company communications (calls, conference calls, and video calls), so I needed to upgrade from my cheaper USB headset (which made me sound like I was in a tunnel to my callers) and buy something more reliable. I noticed that this Plantronic headset touted integration with Lync, so I decided to give it a try....especially since the company was paying for this.I've now had this headset for about a month, and really like it. Lync instantly recognized it upon plugging it in, and all of my callers have commented that I sound great. And it's comfortable sitting on my head hours at a time.I would say the main negative for me is that the microphone arm tends to want to hug my cheek/lips...so i have to re-adjust it a fair amount mid-call so that I don't have any heavy-breathing into my mic.Other than that...it has been great!The most accurate transcriptions I have had in 15 years using Dragon Naturally Speaking. My order was delivered ahead of time which I have found rare. On time is the norm but ahead of time is special!I've used the Blackwire 500 for over a year now in a call center, and I'm very impressed. It's a very high quality headset, and it provides very clear audio as long as you have a good softphone to go with it. The ability to mute inline with the headset is a lifesaver, as you can get a quick drink of water without putting your caller on hold. I'll definitely be using this headset for any future jobs that I have where I have to answer the phone. It's definitely worth the money.The earpads get very hot with their faux leather covers. They can also slide off your head as the faux leather headband offers little grip. These are the non-skype versions and if you use Skype, make sure you get the right set. Overall these are an expensive upgrade compared to my older (broke after 3 years), cheaper plantronics C320 set and in hindsight I should have just bought the same set again.This headset is extremely comfortable for extended conference calls on Webex; sound is clear and I'm easily understood. They have convenient controls for muting audio, and they are stereo with two ear pieces, so good for working in noisy environments. The bass response is I assume deliberately not over-emphasised, so don't expect to use them for replacing your over-ear headphones for thumping sounds - but perfectly good enough for watching youtube vids during lunch breaks.Not a huge fan of this headset.The sound quality is very average, and the headphones go nowhere loud enough for a busy office environment. Not really suitable for listening to music in office.The most annoying think is the horrendous creak that comes from the plastic of the headset.ThanksAaronVery good value for money. The speaker and mic quality are very good - much better than dialling into calls on my mobile. The headset can get a bit uncomfortable if you wear it for a long time, say over an hour, and it can slip around but this may be the ergonomics of my head!Mic too short and as it's on the inside of the headband, too close to your face. The headband is too fat. The overriding reason I returned this was the sound. It's OK when others are speaking but your own voice is weird wearing these, odd echoing. Had to resort to removing one side