I have IRIS registered for more than 2 years - originally issued at LHR T2 Iris office
The system works fine at LHR but on every occasion I have used the IRIS scan at LGW North Terminal it has consistantly failed to recognise me...after its' wasting my time for 3 minutes and then having to get back in the line for a real person - hence now I only use IRIS as a last resort if lines are awful as dont need the hassle!
I think it was a good idea at the time but usual lack of proper implementation and ever more unserviceable machines will see it going the way of most (all) other good ideas to assist the passenger