I also spend huge amounts of time on the phone. My solution was to get a fairly pedestrian Plantronics headset and a Plantronics Vista amplifier. This is pretty much the same kit used by customer service representatives -- not cheap, but built to last. The cord is two meters long, when fully coiled up, and is long enough to reach every corner of my office. They helpfully include a clip that you can use to attach the cord to your belt, which helps avoid whiplash. The sound quality is perfect, and there's no fiddly wireless bits.

The only issue is that when my GSM phone decides to periodically check in with home base (once every few minutes, I guess), if it's anywhere near the cord, the cord will pick up on the noise.