I wanted to get this information out there, as a start, but there are some pieces that I left out. Consider this a TODO list for now. Here's a short list of some of them:
Details about the 'hcidump', 'l2ping', and 'sdptool' tools, and how to use them to debug connections (just didn't have time to go into it here in the HOWTO yet).
A new section about securing the connections, and providing additional layers of security on top of Bluetooth (Bluetooth over VPN, SSL, etc.)
Compilation instructions for the various BlueZ tools, libraries, and userland applications.
Cross-platform Bluetooth configuration (BSD, Windows, VMware)