On a student budget, your best choice of digital back for the H1 would probably be a Kodak DCS Pro Back 645H (yes, it's a bit of a mouthful). Used ones sell on ebay for around $2-3k. It's square format, 37x37mm, 16.7 Mpix, 9 micron pixels.
I have the Mamiya-mount version, the Pro Back 645M, which works really well on my 645AFD. Image quality is comparable to well scanned 6x6cm film.
The 22 Mpix backs are basically the same (9 micron pixels etc.) apart from being 33% bigger in one dimension (48x36mm) and a lot more expensive. However, they have better software support - Capture One etc. - although the Kodak software (free to download BTW) and Photoshop CS2 suit me fine.
Who performs hardware repair on Kodak Backs?
For a student, a little more makes a big difference, but we have had P25 pre-owned backs that we have recently sold between $4,500 - $4,900, which include full 6-12 month warranty and complete case and accessories. Maybe a reach, but just as an option. Purchasing a used back for $2K - $3K might be the only way to go if funds are limited to that budget and you don't want to consider a 5D/D700, etc. But a repair to a used back out of warranty could quickly turn that into an expensive mistake. I
generally don't feel medium format is the best way to go for a student starting out with that budget because funds are limited and repairs can be costly.
Fundegas - you mentioned you were concerned about it as an "investment". Any digital capture device you purchase as an investment will be a depreciating wonderland, so that is a fairly even playing field at that price point. However, if you mean from a budgetary standpoint, then I don't know if medium format is the right place for you at this stage. Maybe it is, but that might come down to your own subjective feelings about the camera options you have in front of you.
Steve Hendrix