I still have the v1 hub, but am thinking of upgrading to the v2 hub. One thing I was looking for is an offline API to get status of devices locally without going to the cloud. I think this would be ideal during power outages (my hub is on UPS), or internet outages, to be able to still get device status.
Local processing is extremely limited at present. Basically the only things that will run are smart lighting with some specific device handlers and a little bit of smart home monitor.
You will not be able to use the mobile app with the hub while it is running locally. (It is technically possible to do that, but that is not how smartthings architecture works). And at present, no custom code of any kind runs, although they have said they would like to add that possibility in the future.
Detailed discussion on local processing
Thanks for the information. Would love to have local processing as well (in case any ST engineers read this).