I just confirmed that JB4.3 on a Galaxy Nexus handles this flawlessly. Connected to my home Wi-Fi network, then left and went to the lobby downstairs without first de-activating Wi-Fi. By the time I'd gotten to the end of the hallway ( ~100 meters ), the Wi-Fi connection had dropped and the phone switched over to the mobile network. Almost no gap in being able to browse the web.
I will try and confirm this on Touch later today.
@Julien
Not connecting to 3G at all ( especially if Wi-Fi is disabled ) is a separate bug. There's a new version of NM in -proposed that fixes what we believe to be the remaining issues with initial mobile data connection setup.
I just confirmed that JB4.3 on a Galaxy Nexus handles this flawlessly. Connected to my home Wi-Fi network, then left and went to the lobby downstairs without first de-activating Wi-Fi. By the time I'd gotten to the end of the hallway ( ~100 meters ), the Wi-Fi connection had dropped and the phone switched over to the mobile network. Almost no gap in being able to browse the web.
I will try and confirm this on Touch later today.
@Julien
Not connecting to 3G at all ( especially if Wi-Fi is disabled ) is a separate bug. There's a new version of NM in -proposed that fixes what we believe to be the remaining issues with initial mobile data connection setup.