I am experiencing the same problem with my new iPhone 6 (16 GB, White-Champagne / Sprint).
The switch doesn't work as it should. (Silent or Ring Modes)
When switched the button doesn't change any setting.
Meanwhile at rare moments (has happened 2 times now) the phone quickly alternates between silent & ring modes (like back & forth 5 cycles within seconds) without any activation of switch or any function.
On hold as we speak with Apple tech agent though (1800MYAPPLE), the agent is escalating the problem to her senior tech supervisor we (the agent and I) are waiting for him/her. Will update with outcome shortly.