I love my 1.8D; I got mine new back around '06 and still use it often on my film bodies (all of which are manual focus, currently). I've even installed rabbit ears on mine so I can use it with my F2S!
It works beautifully on the FM/FE series. My FM2N with the 1.8D mounted will almost fit in a large coat pocket.
For anyone who doesn't like the manual focus ring, be aware that there are many different AF varieties with different focusing rings. Mine is the latest Made in China version and I actually like the manual focusing a lot: it isn't as good as other AF-D primes of the same era, but it's better than many AF-S lenses (I promptly returned my 35/1.8G because I was horrified by the "ratchety" focusing ring). When manually focusing with the 50/1.8D, you can feel the gears, but they are very smooth and they dampen the action a tiny bit. But it boils down to personal preference--I like my focusing rings to be a little looser.
Somebody above mentioned the short focusing throw of AF lenses, but I just did a direct comparison between the 1.8D and the 1.2 AIS and their focusing throws seem pretty close to me! I don't know what the exact degrees of rotation are. The 1.8D focuses closer than the 1.2 AIS.
Optically, the 1.8D is very good. There doesn't seem to be any noticeable barrel distortion (the 1.2 has some). Wide open, the 1.8 is "dreamy" and pleasant--almost reminds me of the effect of Efke Aura, but not as pronounced. The lens can be easily used for macro; I often simply hold it backward in front of the camera for an easy-to-use 1:2 reproduction ratio. I've even been using it for slide copying, although I suspect a real macro lens would be better for that.
Lastly, the 1.8D doesn't mind getting soaking wet, and the front element is recessed enough to keep the glass dry if you're careful. It also seems impossible to provoke ghosting flare.
Ok, just say it, maybe I will marry my 1.8D! One word of warning: if you do get a 1.8, or a 2, or even a 1.4, please know that the 1.2 will never stop calling.