Late 2008 I picked up photography again by purchasing a Nikon D300 with a 18-200mm lens. It was really fun to discover the DSLR possibilities. Almost nothing reminded me from the era of Pentax Spotmatic F or the first Minolta Auto focus camera D7000i.
Extended the number of lenses by purchasing a micro lens and a wide angle. All autofocus. I really enjoyed that camera&lenses. It was accessible and being digital it immediately gave me feedback. It was great to learn new technics and experiment. I still have that camera and still serves a purpose.
Late 2017 I got myself a Nikon Df. It was a camera that had been long on my list. I could have gone for another Nikon camera, a look alike of the D300 with plenty of options and video, but for some reason I did not feel that that would bring me something so much more different.
When I started with the Nikon Df I also tried vintage manual focus lenses. For some reason it just felt right to go back to a bit more analog. The Df is now my ultimate companion.
As the Df accepts Nikkor lenses dating back to 1960, it gave me the opportunity to source rather in-expensive compatable lenses. By experimenting with these manual lenses I also developed my own unique modification to take advantage of fully metering (see services) on my camera.
Other Nikon DSLR camera’s also accept these vintage Nikkor F lenses and as such Nikon truly kept on developing with backwards compatibility in mind. Something to admire in a brand philosophy. Hura.
For me manual focus works in most of the cases. I agree that autofocus has it advantages too, however manual focussing is really satisfying as it forces me into a composition, it forces me to look and to process in my head that final frame. It slows me down and it stimulates my creativity much more then basically point and shoot.

These old Nikkor lenses were precision made: glass, aluminium, brass. Build to last . They are fairly easy to service. The race of cost-down did not play a major role in that time. All parts were extremely well engineered: it was truly quality focus and humble precision mechanics.
Each of these vintage Nikkor (Kogaku) lenses have their own specific picture atmosphere and quality. The quality of pictures that these lenses still deliver is remarkable. Indeed the lens formula might not always be correct and lens coating were basic, but for me it is just these distortions that give pictures just a bit more warmth and depth compared to modern lenses with loads of glass and computer corrected optical designs.

By all means autofocus lenses are great and deliver superb pictures. However if you ever have the feeling that you are hitting a creative ceiling or just bored of point and shoot, do try manual focus lenses on your camera and experiment. I am almost sure that you will discover something new in the way you do your photography. Even if it was to slow you down a bit, to inhale that specific moment and capture that specific picture also in your mind.