This will be mostly for B+W. Bluefire microfilm, Adox, and maybe a couple of others.
Also how about the latest Pacific image scanner, the Pacific Image PrimeFilm 7250Pro3.
This site lists it as having a true 3800 dpi. I do have my doubts though and it is not cheap.
I am interested mostly because you can scan a roll with it.
I have a howtek 4500 but the drum is crazed and its acting up streaking etc at 4000 dpi. Still works good at 2000 dpi though. Setting up and wet scanning a roll of 35mm at 4000 dpi is a real chore and slow at about 20-25 min per frame.