When I say "okay" I mean display accurate information - I'm not really sure what more you can ask of it.
People expect far too much of GPS based systems - they're just not as reliable or accurate as people think they are unless a disproportionate amount of money is put into developing them (which, I'm sure we can all agree, hasn't happened here). In reality, while GPS should be able to tell which station you're at, it's not going to be accurate enough to determine whether, for example, a train is in platform 3 or platform 4 at Manchester Oxford Road. And it's certainly not going to be able to do that before the train arrives in the station!
I think it's necessary to inject a bit of realism here. No, the systems aren't perfect. They are a heck of a lot better, though, than anything on any other trains that operate in this part of the world and - in fairness to Northern and CAF - updates are happening frequently which are steadily ironing out the problems.