Well, I have tried the various drivers supplied by Microchip, and worked a little with the WinUSB example. It's quite simple to manage, if you know a bit of C++. For example, I developed a simple window for setting PWM, and reading voltage and waveform from the PIC.
However, just looking at the CDC - Basic Demo inside the Microchip USB Framework (which uses emulation of the serial port), it should not be too different: the example is a hyperterminal-like window, where you can communicate with the PIC. Upon the communication "engine" which is already done there, you can develop almost every display and measure you'd like, just using the graphic editor and writing few lines of code for the object's callback. In practice you need to find the available COM ports, open them as an object, and then use that object as a gateway to communicate to the USB device. Typically the PIC will receive a byte at a time or an array of bytes (I think that for serial emulation it will be a byte at a time), and then you will write the code on the PIC which reacts to the received data.
The basics should be the same both for an USB enabled PIC and a FTDI+PIC UART, since on the PC side you see a serial port, while on the PIC side you see an incoming data (examples show how to catch them and how to transit back an answer).