I took the same route as Charles -- several years ago I bought a demo 646 instead of a full frame digital camera. Very expensive, but it is still just as useful today as it was then. The great thing about good scanners is they allow you a great deal of flexibility -- you can shoot any camera from 35mm to 4x5.
I will say that I used to use the Minolta Scan Multi Pro, and while I think the 646 is better, it is a tie in sheer resolution. The Imacon is much faster, has better color out of the box, better software, and better edge to edge sharpness. It does not scan mounted slides, which can be annoying if you have a lot of them (or want to keep shooting them).
As for it being practical for high volume work -- well, it was for the entire history of photography before digital. The key now is finding a good lab. There are still some out there. I think Charles is right here -- it is about discretion and reading your negatives -- you don't need to print all of them. Just the ones that are really worth it.
One good way to proof if you don't have a flatbed is to just use a digital camera to photograph the negatives on a lightbox. Just put them in a print-file sheet etc. Once you photograph them, invert them in photoshop, convert to black and white, and voila, digital contact sheet.