So far, it is very cool. I love how I can use natural voice commands and it understands me fairly well, even in crowded areas with a lot of noise. I see it being useful for when I'm driving (integrates well with my car's BT system) It makes doing certain tasks much simpler.
I used Siri to send a text to my sister and that worked great. Then I tried to send a text to my daughter (via Siri) and it kept trying to call her instead. She is going to wonder why she has two hang-ups from me on her phone today! I think the biggest problem is actually ME. I keep forgetting to wait until the microphone lights up to speak. I'll just need more practice.
I love her! She's a comedian. I asked her how old she was twice and the first time her exact words were "I dont see how that's relevant", the 2nd time she said Im not allowed to answer that question LOL!!!!!! Siri recognized my voice right out of the box and knew pretty much 99% of every word I said.
Siri is pretty cool. I like how I can talk in a normal conversational tone and it recognizes all my words. With my Droid I had TO. SPEAK. LOUDLY. AND. PAUSE. BETWEEN. EACH. WORD. to get it to recognize me accurately.
My one complaint so far with Siri - I asked "Where is the nearest Best Buy store?" Siri responded, "I don't recognize Best Buy."