Arca makes some great stuff. I shoot 4x5 film with mine.
IMHO, if you are going to shoot digital and are concerned with tight tolerances and precision adjustment of movements, I'd look at the F-Metric series which gives you geared rise and geared shift, and make sure that you order the Micro-Metric Orbix option, which gives you geared front axial tilt. You can add Orbix to the plain F-Line if you dont need the precision geared shift and rise of the F-Metric.
The regular F-Line compact is more than rigid enough when locked down, and adjusting the basic manual (friction) shift/swing/rise/tilt movements is very smooth. The focusing is also very precise, no concerns at all about being able to dial it in as precise as you'd like.
Where I think you might run into a little difficulty is with using front tilt movements without the Orbix. I find that I use indirect rise a good deal (point the camera up at the subject, then use the bubble levels on the front and rear standards to relevel them both with base tilt). While the bubble levels are accurate, I find it nice to be able to use Orbix to fine tune the precise tilt angle to make sure I have the standards perfectly parallel, double checking focus at both the top and bottom of the ground glass. If you had to do this manually (loosen lock, position the standard by hand, relock, check focus, etc) I think you'd have a tougher time than if you had Orbix, esp for the degree of precision required by a MFDB.
Ultimately, I think the Arca is a great choice. Just be sure to budget for Orbix.
