- More built-in app integration (like GPS). "Remind me to call Jennifer when I leave work" wouldn't compute. The Wolfram Alpha integration is also a nice touch.
- Improved contextual awareness. "Is it going to rain today?" or "I'm in the mood for Italian" don't work for me. I have to explicitly use keywords like asking for a "map of italian restaurants".
- 2-way conversations. I only speak a command and the voice command opens another application based on that command. Siri can talk back to you and resolve conflicts, such as calendar schedule overlaps.
Have we had voice commands on our phones for what seems like forever now? Yep. But that doesn't make me any less jealous of the neat innovations that Apple's done in the speech recognition AI field. Again, a great example of the fierce competition driving innovation, and the consumer wins.
Also I suppose it is kind of a "desktop search" for the mobile phone. Google can not search your contacts and calendar (it could, but the Google search is not really tied into it yet, I suppose).
Siri has been a standout in those areas since before the Apple acquisition. Most people are surprised at just how naturally you can talk to your phone. It's doing more complex work than just passing the request on to Wolfram Alpha.
However, Google has a lot of impressive work in this space, too. I don't think it's long before android phones are this good--they are practically there already.
It's classic Apple: they didn't invent it, but they look like they'll get credit for being the first to popularize it and bring it to the mass market.
I think it is an improvement in the way it is integrated into the phone, but not in AI capability.