The N4 is a significant downgrade from the GN, I sure hope there is something better next year when my contract is up. The non-removable battery is an absolute deal breaker, especially a tiny battery. If I had no other choice I'd consider a RAZR MAXX but I wouldn't be happy but there is no way I would buy a phone with a non-removable 2100ma battery. I'm using a 3800ma battery in the GN. I've just replaced my nearly year old Trexcell battery with a new Hyperion. The Trexcell is still fine but it's weaker than it was a year ago which is just the nature of battery chemistry. The point is that for a trivial amount, $20, I can always have a fresh battery in the GN, with a built in battery you are stuck with the original for the life of the phone which is a self fulfilling prophecy int he case of a phone with a fixed battery.
The N4 also has half the FLASH of the GN, there is no excuse for that. Google has this fantasy that there is seamless Internet access everywhere which simply isn't true. There are lot's of rural areas with no access and in big cities the networks are so overburdened that 4G frequently behaves like 2G.
Finally there is no LTE, what are they thinking. Who in their right mind would replace a 4G phone with a 3G phone.
The only improvements in the N4 don't matter at all, a faster processor which won't be noticeable because the GN isn't processor limited, and a better camera which is nice put hardly a compelling feature.