In no way is the QR a necessity Steve, the main reason I got one is due to a few years working in a garage with a compressor, sprayguns and airtools, it was handy to just click, release, store select new item etc.
A few spare male connectors and you can have one on each item and quick click, to mount or dismount, i find it handy for things like taking my brush to my bench across the room to mix and load paint into the cup without trailing the hose and potentially tripping myself over it or yanking my compressor from it's corner.
Also less wear on tightening the O ring in the screw adapter as you only fit it once
The moisture trap is absolutely esential, after a long session the airline gets hot and condensation forms, I ruined an enamel spray job I was halfway through when it suddenly started spitting water, I was so annoyed but managed to clean and repaint the piece, got a water trap immediately after that, (this is in addition to the one on the compressor btw Dave)