Well, in the department of distortion, I (or rather, Nikon herself) am pleased to say it has almost zero distortion! But, I have previously recommended shooting it at F/2.8 to F/4 for her "sweet-spot" sharpness all the time, unless you really got desperate to shoot at the soft F/1.8 end.
At F/22, shooting, say a sunset (see my D90 gallery), brings about that depth, and color that depict the short light spectrum of orange. Quite cool. Now, though its said by many that the 50mm F/1.8D is but an expensive lens cap for the Nikon DSLR, I still think a HR2 lens hood should be purchased separately to protect this "lens cap". I have found that the use of a UV filter simply introduce too much reflections during night shoot and have since removed it.
In fact, this is what I will do, as I prepare for my upcoming work trip. Add a new lens hood to protect it from sun flare and breathe a new lease of life into the 50mm. At the point of writing, the gross shortage of a Nikon 35mm F/1.8 in my country is but moulding my decision to revert back to my 50mm.