Not sure what you mean.

Anyway OS 2.0 descriptors are a custom USB descriptor that basically tells the device to use WinUSB as the driver. The burden then is in the application that will have to implement the read/writes to the endpoints instead of using higher level functions provided by the custom driver.

If you ever developed software with libUSB, using WinUSB on the windows side makes things super easy for cross platform development, and you don't have to go through all the pain to have a signed driver. Win-win in my book.

yes, you can always use some nasty protocol over HID for your devices. But really most of what i do is one or multiple bulk endpoints so i can achieve full bandwidth (downloading firmware, streaming data, ...) OS2.0 made it possible to do it without having to write and sign a driver