The clock meter to shoot solely with the Nikkor 50mm lens is coming to a thousand for me, and I think its good. These lens are all designed to go beyond 100,000 shots and last for years with good maintenance.
The few feedback to share with the use of this lens is this - its so portable! And in rising occasions, razor sharp. But I must say you need to tweak your Nikon D90 to single focus, 6mm center focus point and all to use the Nikkor 50mm well. Still then, I can't help but notice that the Nikon D90 CAM1000 focusing engine could not nail where I wanted many a times with this lens. Slight variance in where you want sharp focusing seems to throw the subject off.
In the video department, I have been recording up to 20 videos so far with the Nikkor 50mm lens and I must say its such a pleasure to do so with the focusing ring on the outer tip of the lens. Makes focusing smooth and easy. But remember to switch your AF/M flick switch to M on the camera body before recording your first video.
Moving back to the 18-105mm kit lens yesterday, everything suddenly felt so out of place! I guess my mind has been accustomed to the fixed focusing distance of 50mm. Next I notice, the ISO is back in the 3200 range with the kit lens, bringing back the graininess of the image I took with it. Everything is so wierd. I am switching back to the 50mm lens today.