One potential downside to using a GaN charger is that you just might not need it, so it could be a waste of money. The MacBook Neo, for instance, doesn't support fast charging. Attaching a GaN charger won't hurt the machine, but you'll only get a modest speed bump. Consumers do value speed, so GaN chargers tend to be more expensive than silicon chargers. This price difference is shrinking all the time, however, as the technology continues its journey toward mass adoption.