I've been writing about operator cross-network aps for a while, decoupling access from service. We need to see Vodafone 360 on AT&T handsets, and O2/Jajah VoIP on Hutchison 3 phones. It's the only way to build scale against the real Internet application players.
But thinking further, and especially in the light of yesterday's announcement by Nokia about free turn-by-turn navigation, there also needs to be cross-phone applications.
Google has a head start here, with its portfolio of apps available on most devices, not just Android. To compete, Nokia has to follow suit - if it's serious about apps, it cannot just confine them to its own hardware platforms, it needs to port them to Android, iPhone, RIM and so on. Maybe, ultimately even Apple's iron will should crumble, and it should export aspects of its flagship UI to other OS platforms (although I'm not betting on it).
Some of the Nokia apps are really good - the SMS client, for example. Some of the SonyEricsson and Samsung ones too. But if I don't want a Nokia or an S-E phone for any reason, why can't I still have that experience, as long as the hardware supports it?