The Debug view shows each of the Kernels that are running.

A cluster of three kernels connected to the Workbench.
You can set breakpoints in all the typical fashion for
the Workbench. However, any one or some or all
of the kernels might halt execution. You can inspect
the state of the stack at the breakpoint.

A breakpoint in two of the kernels.
You can also run a profile report on the command. Now you get a report for each kernel in the cluster.
Parallel profile report.
To run the parallel debugging and profiling tools you
need Version 1.0 of the Workbench, a beta version
of the parallel computing toolkit and a beta version
of the Mathematica. In the near future the functionality
will become a standard part of gridMathematica.