The UK Border Agency has this to say:
IRIS is currently available at the following UK airports:
Heathrow terminals 1, 3, 4 and 5
IRIS will continue to be available for registered passengers at these airports until after the 2012 Olympic and Paralympic Games.
IRIS is no longer available at Birmingham and Manchester airports.
Registration for IRIS is no longer available. All of our enrolment rooms at Heathrow, Gatwick, Birmingham and Manchester airports are closed until further notice.
In short, Yes. IRIS registration is closed.
In heathrow they are being kept in operation for existing users in the hope that it will alleviate the pressure of visitors attending the Olympics, after which point they will be scrapped there too.
I am a registered IRIS user and in my experience it is a LOT more efficient to come back into the UK using the IRIS machine, however this is primarily because when I get off a packed aeroplane, I am one of the two or three people in the queue for the IRIS machine rather than the hundred or so in the EU passport holders queue I would otherwise have to stand in.
To understand why means understanding some of the politics.
Like every single technological advancement the very first implementation of a monolithic complex system is not likely to be flawless and perfect from day one. Understanding what works well and what could be made better is an iterative process that takes time, testing and careful management.
Unfortunately, however sometimes you get a Tory government who like to march in and announce that anything that hasn't been finished or hasn't had the opportunity to prove its value yet, or simply isn't something they thought of should be scrapped to "save the tax payer money". The conservative's flawless logic being its probably much more efficient to keep our health records on little bits of paper and post them about to each other and not worry to much about border control, we can just keep all the brown people out because we've got the recipe for curry now. ... (life imitating art ?)