I put some more time in, and have (hopefully) turned the 18F4550 USB Interface article into a useful guide for getting started.

I hope to add a new article on using asynchronous PIC-to-PC transfers at some point, including adding an additional endpoint to the PIC firmware, modifying descriptors, and monitoring it in a separate execution thread in C# for more of an interrupt-based approach on the PC side, to get it to the point where from the perspective of the main user program, incoming transmissions from the PIC will simply fire an event.  I've gotten it working now, so hopefully soon I'll have the time to jump from there to an actual article.

Also, on a side note, I discovered that my bootloader could use some more work.  I had issues with programming the config words (which is something I would avoid prefer to not program normally, just to avoid breaking the bootloader if the hex file contained bad values), and I need to make some changes in the fancier version to allow some additional actions (for example - allowing you to program JUST the config words, without affecting anything else)