I use Siri more than I thought. The best way to use it is for reminders. I am not super organized so this really helps me out if I have a quick thought I know I will forget in a day or 2. I also uze it to check the weather in the morning. YesI can open an app, but when I am half awake, holding a button down and asking is super easy.
Hippos, I am lucky in that the voice detection is great for me. I believe it may have to do with your carrier. If you are on sprint, it is probably horrible. I believe that the voice command is quickly sent to a server and processed so that explains why your voice detection may not work well. Google is the same way. Many many times it would not work on Sprint's inferior network.
Now that I have verizon, I can use voice to text anytime..it rarely ever fails. I probably use voice texting more than typing.
as for battery, what I love about the iphone is that I have made zero compromises to save battery besides manually pushing my work email, which I do on every device anyway. my screen is on auto, so it always looks ideal..etc. I think another reason the battery life is so superior is the OS is better developed for multitasking, but also the network I am on rarely has to search for a signal. This is why you dont want to ever sign up for sprint - trust me!!!!