The Google Mobile Blog announced that Symbian and Windows Mobile users can now add multiple search results and content layers -- including Latitude -- to Maps for Mobile:
To get started with Layers on Google Maps for mobile 3.2, hit the "2" key or select Layers in the menu. You can toggle various layers on and off, and you can mash up combinations like friends' Latitude locations against a planned route. Google Maps for mobile Layers is available now on Symbian S60 and Windows Mobile phones, and will come soon to other platforms. The upgrade is available for all countries where Google Maps for mobile is currently available.
This is a mirror of what's going on with the PC side, where Maps enables layers of search results to be shown simultaneously. Right now on Android you can layer Latitude on top of a map with search results.
Google is also making Maps for Mobile more "browse-friendly":
Under Search, you'll find a link to browse popular categories, which helped us avoid the pain of typing on a mobile whilst out on the road (only available in the US and China for the time being).
On Android voice search on Maps works well to minimize typing. It's not clear how voice search will interact with layers in the Android or iPhone versions of Maps.