The Time Capsule problem seems to be related to the internal power supply they have, while the Minis use an external one. So if it does blow up, replacing it should be easy.

From my personal experience, the Minis have been rock solid. From the initial G4, to the Intel Core, Core 2, and now the newest ones with NVidia chipsets, none have ever given me or family members any grief. The only laptop drives I've had problems with have been installed in actual laptops. As far as heat, it's never been something I've noticed, and the fan rarely goes above the stock level even when pushing the system with a VM and some other heavy activity.

Based on the hardware price, it looks like the OS X Server license with the Mini Server winds up to be $200 or less of the cost. Pretty nice discount on what normally is $500 standalone.