I often take photographs on the go, either in my home town or while traveling. Although, I love my D90, I recognize that its weight does bring me down after a long day.
My solution was to get the a Kata neck strap that clips to my bag, thus taking the weight off my neck.
To do so, I have to set my strap to be quite long, kind of too long when wearing it as a sling.
Joby, the folks who brought us the GorillaPod, released this nifty sling strap at Photokina 2012.