I use Siri all the time. It's gotten so that I'm often too lazy to tap or type. I use it for reminders, for alarms, for searches, for reservations, and for a lot more. If I have an idea and I'm driving and don't want to forget it, I'll just say "Hey, Siri", dictate a note, and touch it up later as needed. And in my experience, John Gruber is spot on. Daring Fireball:
I've noticed over the past year that Siri is getting faster — both at parsing spoken input and returning results. I use iOS's voice-to-text dictation feature on a near-daily basis, and it's especially noticeable there. I've been using a Moto X running Android 5.0 the past few weeks, so today I did a side-by-side comparison between Siri and Android's Google Now, asking both the simple question, "What temperature is it outside?" Both phones were on the same Wi-Fi network. Siri was consistently as fast or faster. I made a video that shows them in pretty much a dead heat.
iOS 8's streaming speech-to-text is especially notable. You see it rendering while you're speaking and what's more — you see it changing the words it's already rendered as it gets additional context. Apple's been investing a lot in voice, and it's paying off. Sure, it would be great if they localized processes that didn't require internet access, like setting an alarm, but compared to 2011, it's already night and day. It's gone from punchline to productive feature.
Lastly, a rather obvious but important observation: Improvements to Siri across the board — reducing latency, improving accuracy, increasing utility — are essential to the success of Apple Watch. And — given the previous note on first impressions — it's pretty important that Siri integration on Apple Watch work well right from the start.
It's always been interesting to me that Siri — natural language interface — has existed beside multitouch on iOS. It's been there as an option for when touch wasn't ideal due to circumstance, or optimal due to task. The Apple Watch will likely magnify that — there'll be more occasions when touch isn't ideal or optimal. For some of that, you'll be able to Handoff to iPhone. For a lot, you'll be able to just talk. HomeKit will be similar as well, with Siri moving from secondary to equal or even primary interface. HomeKit on the watch even more so.
Like Continuity and Extensibility and Touch ID, the investment in Siri will likely pay off beyond it's initial implementation.