I currently have a Galaxy S5 and Galaxy Gear. The Galaxy Note 4 and Samsung Gear S were announced at IFA today. I'll certainly be ditching my Galaxy S5 for the Note 4 but will not be going for the Gear S.
The main reason is the lack of a camera. The whole idea of the Gear S is that you will not need your phone. All Samsung had to do was ensure that the social media essentials on the phone were transferred to the Gear S. The camera is one of the most used features on the phone in this day and age. I can't help but feel that this was intentional oversight by Samsung so they could include it on the next release. Marketing tactics perhaps but not good enough. I believe the Gear S will sell very well because of the buzz but I'll wait for the next release when they include the camera, and a few more new features.