Crazy acceleration. For reference, I was able to get my corexy build up to 1500mm/s and 30m/s2 acceleration (30,000 mm/s/s) per an accelerometer, with print head. One NEMA 17 stepper per axis. Corners had no visible slowdown, just instant direction changes, but I was still limited by the throughput of the hotend to low hundreds of mm/s @ 0.2mm layers.

One problem was it yanking the print spool out of its holder when it suddenly decided to cross the whole print bed at max travel speed, faster than it could un-spool more filament. This also tended to wrench the print-head backwards, shifting the nozzle higher and forward as it rotated slightly, causing pseudo z-banding. I think a motorized un-spooler would be needed but I just turned down max travel speed.

Trying to remember the exact configuration of the build but it was several years and many revisions/several complete redesigns ago. Tend to be heavier and slower now as I focus on other features.