The 18-55mm Kit Lens is fantastic optically. It'll last you quite a time and save you some money. The 18-70 is better, but it isn't two hundred bucks better in my opinion. If you got the D50 body-only, I'd buy a used 18-70 for $200 (they're constantly for sale since they're the kit lens on every camera but the D50), but the kit with the 18-55 is a great deal. Don't get any of the other kits (Particularly the 28-80 or the kits with Quantaray lenses), however.
I'd consider going for Body + Used 18-70, but the Kit w/ 18-55 is a heck of a deal. Up to you.