How practical will 1D Mk II be as back-up

Would like to hear from previous 1D Mk II owners how good the image IQ and the noise is on that body as it seems to be a really good buy on the moment. I am looking around for a good back-up body(only 1D/1Ds series) and have looked at the 1Ds Mk I but it had a few drawbacks I did not like.(slow focus----slow write speed---and one or two other things) My other option is another 1Ds Mk II body or a 1D Mk III. As it is only for back-up I do not really want to spend to much but still want a good body. Any information good or bad will be appreciated.

I run a Mk2n - lightning fast AF, high IQ with low noise (don't hesitate to shoot ISO800+, only really "think" about ISO at 1600 upwards). Recommended if you can get one cheap

What is the difference between the Mk II and the Mk IIN, only cosmetic or some serious improvements as I do not see to many "N's" around for sale.

Goshawk wrote in post #6005550
What is the difference between the Mk II and the Mk IIN, only cosmetic or some serious improvements as I do not see to many "N's" around for sale.

Just a few changes for the N such as a larger LCD. I can't remember any other changes between the two but as far as speed and IQ, they are pretty much the same body (if I recall correctly )

The main differences are a 2.5" LCD, better buffering characteristics, new 'Picture Style' image parameters and the ability to write different formats simultaneously to SD and CF cards.

Thanks for the info guys, think I will start searching for a body as I like everything I hear about this camera.