I keep meaning to do a proper thread on this.

I use the Andriod version via my MP3 player, and I've been checking it over the last few weeks. Hat tip to LondonAndy or he may get upset! (He has mentioned it in a previous thread).

There are two parts to the App, the information on gates which is clearly lined up - within 60 seconds or less - with the main customer facing information on the screens; secondly the notifications. The notifications are more flakey, and I'm not blaming HAL for that, the passage of WiFi, 3G and 4G from lounge to aircraft is going to be disruptive. But the gate information on the App itself is quite good, though I would not completely rely on it, it updates just under the flight selected, and you best add to your My Trips tab. I have used it to prevent strolling over to the CCR screens quite routinely recently. It's actually more useful in T3 lounges than T5 (since non codeshare oneworld information can be a bit sparse there).

Also note that additional information on delays is provided in the lounge which is not on the customer facing screens outwith the lounge or indeed on the App. The T5B and T5C screens also give more long term information than the App, for the benefit of connecting passengers.

Once the flight status moves past "Flight Closing" then the gate information vanishes, unfortunately. And they don't - for arriving flights - mention the arrival gate. I've mentioned this to HAL since it would be useful for connecting passengers still on the tarmac to think through their route.