I'd rather have the 18-55 mm because you can take wider photos at 18 mm than you can at 28 mm (it's similar to "zooming out" with any other point and shoot camera), but it almost seems free anyway, so just take this camera + lense. It's a great deal for that camera if you're getting a free lense.
I would probably never use that lense if I already have an 18-55 mm, though. At 28 mm, the 28-80mm doesn't shoot wide enough, and at only 80 mm, it doesn't shoot long enough to be a mid-range telephoto. At least the regular 18-55 mm D50 kit lense allows you to shoot wide at 18 mm, and at the most generally useful range of around 50 mm focal length.
It's your choice, but I'd rather have the 18-55 mm since I seem to either take wide shots at 18 mm (or under 18 mm if possible, which it isn't right now because the 18-55 mm is the widest lense I have
), or I need to zoom very far in (say between 60 to 200 mm), and use the other focal lengths less often. This one does neither, really.
I guess the 28-80 could be used for general photography at family events and holiday parties where the 35-50 mm range is useful.