I shot the 1ds for almost 3 years and then moved the 1ds MKII. The sensor in the 1ds really can't begin to compare with any of the newer APS-C Canon's out there. Plus as already posted, the used 5D MKII is a much better value. They are on the market right now from around 950 on up.
Issues on the 1ds I would consider,
1. Not much good past 800 and 800 is push in most instances. 800 will show considerable noise.
2. shutter count and repair. My 1ds went in 2x for shutter repair, 2nd time it was replaced. The 1ds seemed to have a shutter repair issue.
3. Dust, on the 1ds no small issue. Mine was very dusty and especially in the corners. My 5D MKII's both of them in 3.5 years I have never had to wet clean them. The 1Ds was pretty much a wet clean after every shoot. or every other.
4. No video
5. No ability to really handle a very long exposure much past 25 seconds. The sensor just got too noisy. I also can't remember if the 1ds had a dark frame option, I know the 1ds MKII did. As I recall the 1ds did, but it did not buffer the dark frame like the 1ds MKII and all other Canon's do.
6. Terrible, small LCD, pretty much worthless except for histogram info
7. Bad battery life. I can't remember if they were Lithium but mine were not long in the field. The 1ds MKII had a much better battery life and worked better with the older 1ds batteries.
8. Pretty slow shutter on continuous
9. More than likely will have problems with more modern Compact Flash cards
Image quality is 11mp and in 2003 was amazing. But it's 10 year old technology and when you look at the price of a used 7D, 5D MKII, or even a 5D MKI, they are all better all round cameras. The DxO spec on the 1ds should be pretty low also.
I liked the WB on the 1ds better than the 1ds MKII it seemed to be a more even read out, but I sure would look to a newer used camera system.
I shot with mine for four years and agree with a lot of this - though not with number 2, and personally never had a lot of problem with dust, but then I shoot mostly wider apertures. I also agree that in the most part the original 5D will give a cleaner look and is a more user friendly camera. However the 1Ds is a well built beast and it all depends if you want the weight and build of a pro-camera. I remember when my wife bought a 5D while I was still using the 1Ds. The 5D was so much more pleasurable to use. The controls were much more user friendly for a start. However I then bought a 1Ds mk3 in late 2007 and what a transformation. And it is still my main camera.
In short, the 1Ds produces great pictures, but in my opinion is not much fun to use. Buy a 5d for the same money if you can.