I missed this thread when it was first posted, but I've got some thoughts after using one of these high accuracy mics for ~2yrs, (primarily to measure grade 5 bearing balls 5/32" and below):
1. It was annoyingly difficult to find the rated measuring force of this mic. For a unit with this resolution, hertzian deflections can be a very large factor in the measurement error, so not knowing the measuring forcecan be a dealbreaker.
2. They don't document the anvil material for the micrometer anywhere. It certainly looks like steel anvils, but some people claim they can see a seam where carbide is brazed in. I don't buy it, but either way for a $1600 micrometer I shouldn't have to debate people about appearances to figure out the anvil material. See point 1 about hertzian contact stress: carbide vs steel anvils have very different hertzian contact deflections under the same load, so this is another annoying potential source of error. (Also, why couldn't they be bothered to put carbide anvils on a $1600 mic?)
3. Repeatability and accuracy seem very good, but I wouldn't use this to try to measure 25mm +/- 0.2um, even though in theory it can (of course using it as a comparative tool w/ a good set of calibrated gage blocks is another story, and this is primarily how I use it).
4. Usability is low; it's a standard .025"/rev screw, and it doesn't fit the hand anything like a normal mic. Of course the thermal cover is essentially required if you're doing handheld measurements, and really the right way to use this is as others described, on a mic stand (and in a temp controlled room).
I used this mic to lap a 3/8" shaft to a +/- 20uin tolerance. The lapping was a pain, but the mic made it pretty easy to identify taper and hourglass form errors as I worked. I assume a nice indicating mic would do this similarly, or better. The chamfered anvils were nice in this case because they made it easy to measure shorter sections of the shaft at a time.
I assumed the chamfered anvils were to make it easier to hold the necessarily very tight flatness and perpendicularity tolerances for the anvils. But maybe there are other reasons (maybe off-axis measuring force causes the screw to tip a bit which is an error source?). Either way, they're nice in some instances, and other times (like measuring near a shoulder), they're infuriating.
It's the only game in town for 0.1um resolution micrometers, and I'd rather have one than not if I'm working on a well-funded project that needs a mic with submicron resolution. However my guess is there are indicating micrometers which achieve the similar functionality for less $. Personally I'd choose the indicating mic for my toolbox, and for a company job I'd probably want both.