But seriously, for the folks with Siri, is it that useful? Do you use that often?
I've played around with the voice recognition features of droid, and they're more annoying than useful. Part of it is, the only time I'd really want any of those features is when driving. Otherwise, my fingers are much more accurate than my voice.
Siri has it's uses. Since I got the 4S, I have never once showed up at home, opened the door, said hello to the wife, said "oh shoot", turned around, got back in the car, and went to the Supermarket. Because now, I hang up from her at work, and tap my headset and say "remind me to buy milk when i leave work today". Could I do that on my iPhone without Siri? Yes, but it's slower to tap that out. Could I grab my iPad or my MacBook? Sure, but they may not be handy. Nor would that reminder fire at the precise moment I'm most likely to need it.
Siri's power is combining voice recognition with other features of iOS such as the geo fenced reminders. The data they churn in the cloud doesn't hurt either. For example, I no longer have to say "call john smith on his mobile" to call my dad (that's not his name, btw). Siri understands "call dad" means call my father, since it learned who that was. It also understands that if I don't say otherwise, I wish to use his mobile number. Is it useful? You betcha. The alternative is slower - take phone out of pocket, turn on screen, swipe to unlock, enter passcode if it's been a few minutes, click home if it's not home already, tap phone icon, tap favorites, tap "Dad - Mobile".
Even the weather stuff can come in handy. No, there's no benefit to asking "is it raining", we have windows and eyes. But if I'm packing for a trip, it absolutely is quicker to tap the headset and say "will I need an umbrella this week in Seattle?" then to find the remote, turn on the TV, try to remember what channel the weather is on, wait for the forecast to pop up. It's also, again, quicker than taking out a laptop, especially if it was off already. And it's faster than opening the phone, unlocking, entering the passcode, hitting home, tapping weather, and then adding in Seattle if it wasn't already in there.
The genius isn't MERELY that it understands your voice. It's that some of the early stuff they've already built in is logical and IS faster. "What's the best chinese restaurant near here?" will provide a Yelp list sorted by rating. What's the closest chinese restaurant will sort by distance. And it remembers where you were, so "find me chinese restaurants" can be followed up immediately with "which one is best?"
Reading and replying to text messages is handy in the car too, although not groundbreaking, certainly. Sending emails from the car is pretty nifty too in a pinch.