What is an infill plane?

What is an infill plane? They're beautiful, but do they work differently than other planes? Is it a type of tool that a hobby woodworker like me should own?
—Marvin Black, Memphis

At its core, Marvin, an infill plane consists of a metal body with wood components tightly fit ("infilled") into the interior voids. These handmade tools come in different styles (smoother, shoulder, miter, and panel), and perform essentially the same functions as antique and modern cast planes.

Because most infills, especially pre-World-War-II models, use dense, heavy wood species, such as rosewood or ebony, they have greater mass to help power through cuts. But that's the only advantage an infill has over a "hollow" cast-iron plane. With limited, fussy blade adjustments, an infill can be frustrating to use until you become experienced with it.

And because you'll pay two to three times more for an infill plane than for a new or antique cast model, we'd have a hard time recommending you get one. We suspect that many people who buy infills treat them as collectibles rather than working tools.