I assume it's not mentioned to keep the article brief, but most devices these days support MTU sizes greater than 1500 bytes. Jumbo Frames[1] allow for ethernet packets of up to 9216 bytes.
Since they have to be fragmented back down to 1500 for devices that don't support them, however, it's typically only used in closed internal networks, like a SAN. People typically see about a 5% to 10% bump in performance.