What can I say? This pedal lives up to the hype. Like most pedals of this vintage, the analog circuitry is a touch noisy, but a little noise is OK, and there are many post-production tools that can eliminate it after the fact.
I have tried many analog Delay pedals, including the MXR Analog Delay, Boss DM-2, and Ibanez AD9 (this is the one I use now), and the DM-1 sounds at least as good as any other. Capable of producing a range of effects, from simple slap-back delay to full-blown repeating delay (max. 300ms), the Delay Machine does exactly what you want it to.
However, there are some things that stand in between the Delay Machine and everyday use. First of all, they are super-rare and super-expensive; this makes getting one a lot more difficult than some (maybe all) delays. Secondly, the pedal is HUGE, about 6"x10", and has a built-in grounded power cable resembling the one on a refrigerator. Finally, the pedal is a little touchy because of its age; the pots require regular cleaning, and I can't help but worry that it might just give up the ghost one day. Because of these issues, I would recommend the DM-1 for studio use before I would use it live.
The sound: Warm, warm, warm. The DM-1 uses the Reticon R5101chip at the heart of its circuit, and this (now discontinued) CCD processes the signal into 'bins' to simulate analog conversion, and allow the circuit to be manipulated to produce the delay effect. The DM-2 and the famous "green" MXR Analog Delay also use this processor, with a similar effect.
Verdict: AWESOME! If you have one, congrats! And if you don't - allow me to recommend the Ibanez AD9 or the Boss DM-2, both of which have similar features, a similar sound, and are a lot easier to get.
$400-600 depending on condition/modifications
-Great warm analog sound
-Very solid construction
-A little noisy
-Limited delay time
-Too big for a pedal board