What's truly different about Google Now is that it can be proactive, showing you "cards" (nuggets of information) you didn't ask for and alerting you on its own initiative to things like the changes in the weather, people's birthdays, reminders from your calendar, directions to places it knows you go, and places to go nearby.
Even before this week, Google Now users could use the voice command to search the Web; send email, texts and Google+ posts; make calls; get the time and weather; check the calendar; get Maps directions and find nearby restaurants; do math; and set reminders, timers and alarms.
All of this is streamlined by the fact that Google knows you well. For example, the first time I said: "Google, call Kenny" it knew I was talking about my son, it knew his phone number and just placed the call for me. There was no voice training, no relationship-setting -- nothing. When you ask for weather or directions, it tells you based on your current location.
One of my favorite features is that you can say "Google, play 'Sweet Home Alabama'" and Google Now will simply play the song from YouTube. It's very hard to find a song that isn't on iTunes, so it will play just about any song -- or any video.
Another cool thing is that you can say "Note to self" and whatever you say after that will be sent to you (you can set it to send self-notes to Evernote, Keep or email).
In addition to these existing abilities, Google this week announced several new ones.
The best is geo-fenced, or location-based reminders. You can say, "buy milk, bread and apples next time I'm at Whole Foods," or "Try Billy's Bakery next time I'm in New York" and Now will hang on to the reminder until you go there.
Google also added new abilities to interact with public transportation and entertainment information. For example, if you buy movie tickets through Fandango, Google will find the confirmation in your Gmail in-box, then tell you (without prompting) via Google Now when you need to leave for the theater based on current traffic conditions.
You can phrase a public-transportation query vaguely, and Google Now should know what you're talking about. For example, you can say: "When does my flight leave?" and Now will tell you the time (based on the confirmation in your in-box). If your flight is canceled, Google Now will alert you.
For the month of May, I've been on a "Google Now diet" in which I use the service exclusively when I do a long list of tasks (basically all the things Now is supposed to be capable of). Google Now has completely changed my relationship with my phone. I'm talking to it constantly and hardly typing anything.