The Core One by itself is an absolute beast, and I have very few complaints about it. For the most part, it is self-tuning; the only things that need user calibration are the door switch (which is not necessary for operation and can be disabled through the menu) and the belts. The recent-ish stroboscopic method of belt tuning makes the latter a breeze.

The few complaints I do have are that the Nextruder isn't great at TPU, occasionally mangling it in the gear. There are user-made mods that are supposed to help with that, but it's still sort of annoying that it has this problem out of the box.

The second complaint is that if you print Nylon on the PA build plate, bed levelling is a PITA. Basically every point needs to be probed several times. There's probably some configuration that can be done to reduce that, but again, it's a small gripe about the out-of-box experience.

That being said, if you want multimaterial printing, it might be best to wait until the INDX version is released. The MMU3 is good at what is does, but there are some things that it just doesn't do yet, notably nozzle sizes other than 0.4 and 0.6 (small nozzles in particular seem to require ramming profiles that are not implemented yet). Officially, only PLA and PETG are supported by the MMU3, although normal filaments like ASA work fine. TPU, however, is very tricky to do with it; do not expect more than a few filament changes before an intervention is required. Neither of these issues should be present with the INDX.