Son,
I've been dabbling with multiple formats, and I've found different setups to be the sweet spot when it comes to digitizing.
For MF I get great results with Nikon 8000, wetmount and multisampling (in fact better than low-end drum scans - keep reading). There are several good solutions for MF scans including of course the Imacons which have a great way of achieving film flatness.
For 4x5 there are also several good solutions. I don't have that many 4x5's so I scan them the same way as my 8x10's.
For 8x10 it is tricky. I have tried (still have) a Microtek 1800f that leaves me unimpressed, as only the center of the scan bed gives good results. Also, due to the lengthy time of an 8x10 scan (especially with multisampling) the CCD heats up and towards the end of the scan the blacks are green. Most flatbed scanners without dedicated active cooling seem to have this problem.
Beginning of last year I bought a Howtek 4500 drum scanner on Ebay, got it shipped from Canada. At first it didnt work when I powered it on, but a few kicks (!) and it started. I took it apart and cleaned all the electrical connectors, and it has been running fine ever since. Before moving back to Europe this spring I took the Howtek down to Aztek for full mainenance service, so it should be good for a few more years. Total cost so far has been $1500 puchase with shipping (incl 4 drums and mounting station so it was a steal), $1400 maintenance at Aztek, and about $800 for the ionizing gun setup (which is great for dusting off anything including DSLR sensors, as well as getting the static out of my girlfriend's dress).
Comparing drum scanning workflow to scanning with my Nikon 8000, it's quite a difference. For the drum scanner, getting rid of as much dust as possible is the key. I have a ionizing air gun called Top Gun to neutralized static electricity. With the gun is an air compressor, and a special air filter to make sure the air is perfectly clean and dry. The next step is wet mounting, which is an art form by itself. Once wet mounted, the scanning process is fairly straightforward, and the film comes out of the wet mounting fluid cleaner than it was before, no worries there.
The Howtek 4500 scans at 10 bits per channel, which is decent but not great. There is no way to adjust exposure before digitizing (unless you get Aztek's expensive software) so reaching into dark areas is still difficult.
Note that this is 10 _linear_ bits depth, some people confuse this with gamma-encoded bit depth. 10 linear bits of density corresponds to 10/2.2 bits of density in AdobeRGB space. (Don't get this wrong, it's still a good idea to edit in 16 bits!!!) My Nikon 8000 with 16x multisampling does capture 14 true bits of linear density, it's actually quite impressive (but a 6x9 scan takes 3 hours...)
Anyway, to summarize, I would not recommend getting your own drum scanner for 4x5 or smaller formats, the effort involved is too much (plus you have to dedicate a room in your home to be your dust-free zone). Getting the scans done at a scanning service might be worth it. For 8x10 I have not seen any other good solution than drum scans, perhaps a high end flatbed would be good too.
Hope this helps sorry about the excessive ramblings,
Lars