One more thing I'll say about Capacity Planner is that you shouldn't always take the inventory data that it gathers as fact. Often times a spreadsheet maintained by the IT staff will be just as much or more accurate. As an example, I recently completed an analysis in which the environment had non-standard (self assembled) servers. On nearly all of those servers, the Data Collector reported their RAM as having 8 times as much as it actually did. 8GB systems were reported as having 64GB which totally threw off the consolidation estimates. As the outside consultant I didn't know that this was incorrect data so this delayed things a bit.

Great post. Hopefully this becomes a standard post for CP troubleshooting similar to Duncan's esxtop post for performance analysis.