Many amateur golfers do not hit some of their irons as far, as accurate or as consistent as they would like. Many of these same golfers have tried high-lofted metal woods in place of these difficult to hit irons. Unfortunately, these traditional metal woods are not the answer for everyone since they can be difficult to control distance and direction. Thus, you are seeing more and more of the ironwoods in golfers' bags as an even better alternative to traditional irons.
Though some of the ironwoods look more like a wood while others look more like an iron, most have a club length that is shorter than the equivalent wood and longer than the equivalent iron. For the best results you will want to swing these ironwoods more like an iron instead of a wood. Typically, irons are swung with a descending angle at impact that creates a divot; whereas woods are swung more level at impact, sweeping through the ball at impact (matting down the grass, not taking a chunk of grass). In other words, it is encouraged to take a shallow divot when swinging an iron-wood. Many golfers tend to hit thin shots with ironwoods when they try to sweep the ball off the turf like a traditional wood.
Many golfers today do not have to make the decision whether to muscle an iron or finesse a wood because ironwoods allow them to take their normal swing and achieve the necessary combination of power and control.