The problem with knots is that they resist drilling and screwing. The problem with new growth is that the pith is the weakest part of the wood, and new growth has the most pith.

Still, it's not a weak and terrible pos wood-like material like 1990's MDF, it will probably be ok for most uses as long as the grain direction is respected in regards to shear direction (typically you want the grain direction to run perpendicular to the shear forces) and everything is properly braced.