I just bought my 64gb 4S yesterday and Siri hasn't worked at all in the 24 hours I've had the phone. I am on Verizon. I've done a soft reset, a software reset (via iTunes), and I have reset the network settings and nothing has worked. I have tried it on wifi and on the cellular network. When I called Apple tech support, they basically said "tough ****. It's in Beta testing". Not really sure about you guys, but that seriously ****** me off. Like someone else had said, using a feature that is in testing as the main selling point is underhanded, and to be perfectly frank, complete ********.
I've also had issues regarding reception; it drops signal unexpectedly, then jumps to "extended" or "roaming" or just goes to "no service" after having full signal. I am planning on heading to the Apple Store in the next couple days and swapping the phone unless it starts working properly. The signal issue seems to be happening less and less frequently, but in all honesty, it shouldn't be happening at all.