Judging by the US$ cost of new cameras, those prices sound very good to me, but then I'm not totally sure about what constitutes a good deal over there.
The *Ist DS and DL are both 6mp dSLRs from a couple of years ago, released around the same time as the Canon Rebel XT and Nikon D50... they are still good entry-level dSLRs and use the same Sony sensor which Nikon and Pentax continue to use today (in the D40 and K100d respectively). They are very similar in most ways, and I can only think of two main ones...
The *Ist DL has a larger rear LCD screen of 2.5" compared to 2" on the DS.
But the *Ist DS uses a pentaprism for the viewfinder, whereas the DL uses the cheaper pentamirror system.
Personally I think the DS is definitely the better buy because of the brighter viewfinder... it might have a smaller LCD but IMO the viewfinder is more important, a brighter one being better for composing and for focusing (especially for manual focus).