For digital IR I have used a Sigma SD14, a few digital point and shoots and this Nikon D70s. The D70s is by far the best of those. It is sharp and the older lenses have IR focussing marks which are really useful. I do intend to switch to Canon, perhaps a 20d, simply to take advantage of the lenses that I already have for that system. Mind you, you never can tell with lenses for IR. Many of them suffer from glare spots (see below) and you can’t tell until you’ve tried them. The Nikon lens on the Camera below is in fact excellent for IR. It’s an older 35-70 Zoom.
This camera doesn’t have an IR filter over the chip, so you can’t see through the viewfinder when using an IR filter. But this does mean it can be used for astronomy as a full spectrum camera and with an IR blocking filter, can also be used for normal photography.
I sometimes use a vintage viewfinder that clips into the hot shoe. This has zoom and distance settings on it so you can see the picture you are taking. As a package, this then can’t be beaten - see the second image below.
One more thing about the D70s which is very useful: you can control the flash manually. You can set it to 1, 1/2, 1/4, down to 1/16 I think power, and this can be used for IR as well of course.