Conclusion: The HP Z200 is a small form factor workstation desktop for the space-constrained user with a "must-do-now" workload. It's much pricier than a regular business or consumer-grade system, but as they say, you get what you pay for.
Pros: Compact. Powerful. Expandable. HP Performance Advisor. No bloatware.
Cons: Only takes half-height expansion cards. No room for extra hard drives. No eSATA or USB 3.0. Expensive.