"Great sound for calls, comfortble; horrible durability"1.5 starson by TGA29
Pros: Sound quality, comfort. Used primarily for conference calls, many hours per day. Must have clarity incoming and outgoing and these did a great job. Was not using them for music much. Superior voice quality and clarity compared to average headset.
Cons: Durability POOR despite careful handling. 1st pair: 1 channel went out at 6 months, Klipsch sent replacement. Repl'mt pair: 1 channel out at 5 months. Software: issues with inadvertent toggling between calls and music.
Summary: Using App's settings for customizing buttons, button toggled between phone and music: would start playing music if I accidentally clicked button while on a call on my Evo 4G, which happened frequently when either attempting to increase volume (long click) or handling to adjust microphone position. Had to remove Pandora from phone to prevent this embarrassing problem from occurring on business calls. (clicking the single button takes you out of whatever app you're in, on Android - google for digitaltrends' old review for details.) Also, make sure you check for current conflicts between software and various phone models on the klipsch website.
When 2nd pair failed (still less than a year after original purchase) I opted for Bose MIE2 instead, with a 2 year in-store replacement warranty ($20 on $129 set at Fry's). If you're going to invest in the Klipsch S4a's, do yourself a favor and get the in-store tech warranty because you'll probably need it.