Strictly speaking, MDF falls somewhere between mere particleboard and so-called high density fiberboard. Particleboard itself is unsuitable for many home renovation projects, as it will flake apart at the slightest touch.
MDF is extremely heavy to handle, and it will dull your saw blade. Not only that, but it will chip apart when you attempt to screw into it.
MDF will swell and warp when water contacts it. Also, MDF may contain formaldehyde, a substance hazardous to your health.
MDF does have value because it does tend to be cheaper than natural wood. On top of that, when you fully encase MDF (as in the case of a solid-core wood door), it is practically indistinguishable from natural wood. Also, MDF can be quite dimensionally-stable.
Finally, MDF may even be considered an eco-friendly building material, since it uses up waste wood.
