DX -- Indicates a lens designed to cover the smaller image circle of the
digital camera bodies. May still work on 35mm bodies at some focal lengths.

http://www.bythom.com/lensacronyms.htm

It will work just as good for any D50 or D70 and yes you will save money.

I have the 70-300G for my D70 and love it.  What a great buy!  Since I
saw the first "X" or whatever the particular manufacturer uses to
designate digital only lenses, I've been wondering why would you ever
buy one?  Four or five years from now when DSLR's with full sized
sensors start to get affordable, what do you do with your collection of
"X" lenses that won't work or vignette with a bigger sensor?  Maybe I'm
missing something?