Siri is powerful, but many say that Google Now is simply better. The new conversation mode for Google Now is embedded in Google's aforementioned new Search app version, which brings a number of other changes, as well.
3.1.8 shipped in the Nexus 5 and KitKat (Android 4.4), so the new release brings that same functionality to all devices running Android 4.1 or greater (Jelly Bean; Ice Cream Sandwich and Gingerbread users need not apply).
The conversational aspect appears when you give Search / Now certain commands but are a little too vague with them. For example, When give the app a rather obtuse command, like "send a text message," and it will ask who the recipient should be. If you state a name, it will then ask what the message should be. Once it has all the required information, it will ask if you are ready to send the message.
In addition, Google Search 3.1.8 houses the Google Experience Launcher (GEL), which means any Android 4.1+ user willing to sideload a small app can have GEL, now, as opposed to those with KitKat.
Previously, only those users with KitKat -- which just began rolling out to the Nexus 4 and Nexus 10 -- along with the Nexus 5, could use GEL (although the 4 and 7 needed the add-on APK). The update removes that requirement, and it also fixes the GEL layout on tablets.
Google didn't even mention the conversation mode (and certainly not GEL) in its blog post about the new release, instead focusing on new cards and information from its recent Waze acquisition.
If you’re a fan of a particular blog, the Website update card can bring you things like the latest post so you’ll never miss a story, and the News topic card brings you fresh articles from the web on topics you care about. The What to watch card gives you Movie and TV recommendations when you’re staying in.That final tidbit about in-store pickup could probably apply to the iPad mini with Retina display, which currently can only be found in Apple stores if you buy online and use "Personal Pickup."
There are a few other great additions in Google Now with today’s update: you can see traffic incidents on your commute using real-time data from Waze, set repeat reminders, get real time scores for rugby teams, and also see when your packages are ready for in-store pickup.