Yes, and that does give the same field of view as the 50 when used on a crop sensor. The reason I like the 50 on a cropped sensor is it gives the same field of view as the 85 1.8 does on a FF camera, perfect for portraits.
Excellent reason IMHO for wanting the 50mm. During yesterday's photowalk, we of course we're talking about gear. One of the pros told someone that the only reason to upgrade a body was when you realized it was limiting your vision and/or creativity. Sounds like you might be there?
Not that I am trying to talk you into a new camera but with the replacement for the D90 coming out you might be able to pick one up used soon for a great deal. Would be a nice upgrade to your D40 and allow you to use those lenses without a SWM in them.