The Good- The Plantronics Savi 7220 (See Savi 7210 for single speaker version) is the replacement for the CS520. Dual speakers make this headset ideal for louder working environments, so you keep both ears covered to zone in on your calls. Improved headband design, noise canceling microphone and softer ear cushions, the Savi 7220 will be comfortable all day.
The Bad- If you don't like a headset that covers both ears, this model won't be for you. In addition, this is a desk phone only headset, so you won't be able to connect with a computer or mobile phone, if your needs change in the future.
Overall- For a desk phone only headset the Savi 7220 is a very good choice for those working in loud environments. DECT technology, 12 hour battery and 350 ft wireless range gives you plenty of freedom to multitask in your office hands free.