It's worked every time I've used it 100% (I don't know how many times that is, but it's in excess of 15 times - not a huge amount of use, but significant). Today, T4 was a scrum at European passport control but 4 people in the Iris queue, was through in less than 5 minutes.

Really, the organisation and staffing (just queue management would be a start) in that area could really do with some attention. Someone guiding people to the right place, informing them of the Iris availability (or inavailability). At least in the US immigration, the area is staffed and your are instructed (in dictator style) where to go.

Shame BA cannot, and just does not seem to be interested in priority bags... It really annoys me when they never deliver on this service. T5? Yeah, right...