The best controller, at least for me, is the Dualshock 4. It just fits my hands just right. So even on PC games, I always used the Dualshock 4. Unfortunately, Sony never really officially supported the DS4 for Steam games. And why would they? It's not their platform, after all.
When the official USB wireless dongle for the Dualshock 4 was announced, I was stoked! Could this be it!? Could this be Sony officially supporting the Dualshock 4 on the PC?! Alas, it is not to be.
I mean, you always could've used your Dualshock 4 on your PC games. You just needed to install 3rd party apps like DS4Windows or some other kind of input mapper. Installing those extension apps always felt messy to me. I wanted a clean solution from Sony.
The dongle is mainly just for a clean way of pairing your DS4 to your PC for PlayStation NOW and PlayStation Remote Play. Nothing else, officially. If you want to use the DS4 for Steam, you'll need Boganhobo's update to DS4Windows. I was able to use it successfully with games like Marvel Heroes 2016 and Shadow of Mordor, though since my motherboard has a built-in Bluetooth adaptor, I really didn't need the dongle at all.
There are rare games that use and support the Dualshock 4 input - like Batman: Akrham Knight. For those games, you'd actually have to disable DS4Windows and plug your DS4 in via a USB cable.
The USB dongle use is very specific. If you want to play PlayStation Remote Play or PlayStation Now (which we don't get here in the Philippines), and you want to do it wirelessly and you don't have a Bluetooth adaptor, then that's the only time you should get this dongle. Otherwise, stay the hell away from it.