I agree with the IRIS comment, those machines are always breaking down!
I am annoyed that when coming through T2 the other day there were 20+ desks with only 2 dedicated to UK/EU nationals. Other countries have more for their own citizens, especially now that they are going through this "extra care" security and actually taking time to look at passports.
Lack of a fast-track for UK/EU arrivals, but I don't always fly business class so would prefer for them to get the balance of open desks right. It irks me that as a UK citizen I cant use the fast-track, yet a non UK/EU citizen can.
Having said that, my last few experiences of the immigration officers have been positive, normally they say good morning, or greet you.