Delay effects, digital and analog, are all over the JD records. Tons of it especially on 'Autosuggestion'(guitar, drums, like the way the drums have those multiple sectioned repeating effects, some of which are held and mixed with feedback from the other heads for that big, weird sound), 'These Days' and all the drums and ambient sounds on Unknown Pleasures. Like, listen to the snare drum on the third beat of each measure in the verses of 'New Dawn Fades', it is heavily delayed, and Hannett constantly varies the delay settings in a similar way to dub reggae, which is probably where he got it. Barney was a heavy user of delay in his guitar rig, too, which was quite possibly a Hannett influence (I don't think he used them before they worked with Hannett).
The pitch of Ian's voice was reportedly slowed down in the studio simply by changing the speed of the analog tape deck, which is a cool effect and very transparent compared to actually running a voice real time through a device that can pitch shift. At that time the only practical way to do that was with an Eventide Harmonizer, which is what they used in concert. It is pretty easy to hear the difference, the harmonizer kind of dirties up and compresses the sound a bit in addition to pitch shifting it, whereas the studio recordings are a lot more subtle (that is, as an engineer who has heard a lot of stuff I can hear that his voice on Unknown Pleasures was pitch shifted, mainly in the way it changes the sound of the decay of the held note, but most listeners can't tell).