INSIGHTS
The Hitachi 7K60 was the fastest alternative internal drive. If you find the 60GB capacity too confining, the Seagate Momentus 5400rpm drive provided much more speed than the stock drives in all except the Photoshop test while providing greater 100GB capacity.
Another way to add speed to your Mac mini without cracking open the case (and risking warranty nullification) is to attach a fast drive to the FireWire 400 port. That's exactly what we tried. Not only did we test the same drives externally as we tried internally, but we added the fast Maxtor DiamondMax 10 300GB 3.5inch 7200rpm drive to the mix. It added both speed and mucho capacity to the Mac mini system. Too bad the mini doesn't sport a FireWire 800 port.