The 1Ds is a little old and quirky (so-so battery life, not very good at higher ISO, can't zoom on the LCD etc) though it still produces good pictures. The 1Ds Mark II is an entirely different animal; it's 5 years old now but still cranks out SUPERB images, even at higher ISOs. Super fast AF, built like a tank, great viewfinder, just an awesome camera. Yes, I have one and yes, I am biased.
If you read FM (fredmiranda.com) much you can see quite a bit of discussion about these cameras, including comparisons to more recent gear; one guy posted ISO 100-3200 comparisons with the 5D Mark II and the 1Ds II held up incredibly well.
So go buy one. Now.