Reading between the lines of gmueckl's post a little, it's not hard for most people, but there are several aspects to the process that would challenge people with one or more disabilities:
> Mobility and dexterity, being able to dial the dials
> Memory and cognition, remembering where you are in the process
> (he didn't mention this) Sight, being able to see the dial accurately and consistently
I was also able to use the dial phone as a kid, but I'm glad it's gone, too.
(By the way, is there any way to make a bulleted list in hackernews text?)