I am going to say no. This post by Boris on TheNextWeb asks whether Siri is becoming just a gimmick. In the article, he also brings reliability into question. Yesterday, I had a conversation with a coworker that finally switched to the iPhone from a dumb phone after asking me questions and debating about it everytime we saw each other over the course of a year. He finally bought one when the 4S came out. He told me that he loved his iPhone, and couldn't even imagine not having it. He then said, "I don't really use Siri that much though". When I asked him further, it turns out that while he doesn't hold it up and ask questions, he does use it to dictate texts and emails many times a day. I do the same thing.
I was reminded of this conversation when I read the above article. I don't experience any where near the downtime or reliability problems that are mentioned in the article or by Marco Arment in his response.
My most common use scenarios are:
Texting when my hands aren't free Listening to texts when I can't look at my phone. Sending short email messages Starting timers Setting alarms Adding items to my calendar Adding to-do items and grocery items to my list
I'm a bike commuter, so the hands free, eyes free thing is really, really useful every day.