[praxguy]

Haven't tried this yet, but here's the powerpoint slides from the NSCA National Convention

Basic points

• Cluster sets are a way of partitioning mechanical work in a work out. Rather than completing the set and taking a rest interval, you take short rest intervals between repetitions (IE broken reps) and a longer rest interval between sets. This helps preserve force output, power, and velocity.
• Velocity and power tend to really drop off after the 3rd of 4th repetition, so having a intraset rest helps preserve the overall quality of the work.
  Form of movement is preserved by utilizing the cluster set method, decreasing horizontal bar displacement during weightlifting movements like the power clean. This will likely translate over into less technical movements like the typical powerlifting movements.
• Cluster sets change the training stimulus and allow for a clear methodology to develop strength-endurance and power endurance.
• The continuum for intraset rest periods is much as you would expect. Shorter intraset rest periods could be a mechanism for str/pow-endurance and hypertrophy, moderate intraset rest for strength, and longer intraset rest for power. In the same fashion, rest periods between sets is longer along the same continuum.
  

If you want some of the nitty gritty, the slide deck is littered with citations.