Shun Cheung , Nov 20, 2006; 10:18 a.m.
If your Nikon lens is a manual-focus one to begin with, there is no AF with any SLR or DSLR anyway. Therefore, the fact that the D40 cannot AF with non AF-S lenses is irrelevant in this case. With the D40, there will be no metering just like with the D100, D70/D70s, D50 and D80 (as well as the film based F80/N80, etc.).
The viewfinders on the D70 and D50 are rather poor. That problem bothers some people to no end and doesn't bother some other people much. Only you can decide which camp you belong to, or most likely, somewhere in between.
I have no first-hand experience with the D40's viewfinder.