I think Matt is right, that it is designed for small dental x-rays. I don't see how it could handle 4x5. X-ray film uses basically the same chemicals as photo film, so you'd be fine with standard photo chemicals, but I don't see how you could control the development timing. It looks like it just passes each sheet through each tank at a standard rate.
If I found one of these for cheap at a thrift store I definitely take it home and play with it, but for $250 I'd put the money toward a Jobo...