The 1Ds tops out at around ISO 400 with decent image quality. You could get better,far better, image quality from a first generation EOS 5D. Not that it would be a body upgrade over much of anything, but the 5D's images would be nice.
Personally, I don't think buying high-end used equipment from national web stores is a good idea--the prices are far too high at the very largest web outlets. The last 1Ds I saw for sale used at walk-in retail was about six months ago, and it was $1,100 or Best Offer...at a "real" brick and mortar store that is not visited by 10,000 people per day, the actual worth of an original 1Ds is not anywhere near $1599...not even close!