Eh, it's no speed demon, but it's quicker than driving to the LHBS for over-priced, poorly-crushed grain (YMMV). With a decent drill I can get thru 12ish lbs in a couple of minutes...
Readjusting for various malts is a pain because there are no marks to indicate the gap.
This is true. Which is why you set it and forget it. I BIAB, so super fine crush doesn't worry me. I tighten the plates down to just almost too tight for them to turn against each other... They clatter together when no grain is going through. Took maybe 5-10 minutes of fiddling at the beginning and that was it. Now, this might not be suitable for "regular" mash tuns, I guess. Maybe too much flour and husks that are too shredded. But there's no need to change anything for barley, wheat, rye, etc. For BIAB the tight setting works just fine. Been using mine for years and feel no need to upgrade to a roller miller.
Nearly every LHBS has a better and free-to-use mill.
Ha! Better? Perhaps... Free to use? Probably.... Will they let you adjust the mill gap? Will they let you double crush? That 2nd one is what pushed me to get my own mill. The LHBS crush was just meh, so I compensated by running the grain through twice.... Until they changed their policy and forbid double crushing, and were rude @-holes about it, to boot. Oops! I now have my own mill station and buy bulk grains from some place else. Major (and consistent!) efficiency boost just switching to my own crush.
I do advocate buying your own mill for consistency and predictability, but the Corona is antithetical to these goals.
I disagree with your assessment of the corona. Now if offered a choice between a free Monster Mill/Cereal Crusher/other-3-rolller-mill and a free Corona?
No competition... Hello free Roller Mill! I'm not trying to assert that the corona is a "superior" option. I just throwing out that for $25 it's a viable budget option that can get the job done, especially if you BIAB...
Perhaps if I brewed more often, or used a cooler (or other "normal") mash-tun, I'd be singing a different tune. But I've been quite satisfied w/ muh-muh-muh-My Corona for many years now.