I do voluntary work with GD and know a couple of people who are regular fliers on short haul flights with their dogs - they are highly trained to do their stuff on command (the dogs that is!). We board them while they are training and they manage to go eight hours without making a mess of where they sleep and I've never had a guide dog that has so they should be able to cope with a range of long haul flights.
I think this is a much needed development and it saddens me that people are not very tolerant of the needs of others less able than themselves.