Good Points: I think the best aspect is the single knob. Other phasers have multible controls, with obviously color the sound in ways much different than this, which is probably why I've not been able to replicate this sound with the others. Being encased in metal, it's very sturdy. I'd never had problems with mine. The worst thing that happens is your battery dies, no big deal.
Bad Points: With these older pedals, the only way to get to the battery is to remove all 4 screws holding the base in place. But with that being the ONLY down side to this pedal, it's really a petty thing to point out.
Good Points: Simplicity. Only one knob, but the variablity of speed is very wide. You can create very subtle to quick pulsating phasing with this pedal. Housing is durable and connection points are high quality.
Bad Points: For a pedal that is 30 years old, it only has one problem. The pot is a little scratchy. It used to pop a little bit when you would turn it off/on, but that has since disappeared.