The main trade-offs are speed, focus range, and load capacity.

Because the adapter has to move the entire lens, autofocus is generally slower than a lens designed with its own focusing mechanism that only moves small internal elements. The adapter also has limited travel, so it may not be able to cover the full focusing range for every lens. In some cases that can mean you lose access to one or both focus extremes, depending on the lens and starting setup.

Lens size and weight matter too: larger, heavier lenses may be too much for the adapter’s motor to move reliably or quickly.

So the concept can work well and is very clever, but compared with native focusing systems the practical downsides are typically slower AF, possible limits in achievable focus distances, and reduced suitability for heavier lenses.