Hey.. i saw that when reapers were first announced to have charged bombs, the time needed before exploding was long, and was noted as more useful against buildings.

well, in BR 2.. the time needed for the charges decreased greatly

any news on whether or not the charges are currently intended for use against infantry or only stationary targets like before?

The Reapers' mines are definitely multi-purpose. They work excellent against grouped up units as well as stationary defenses and hitting strategic locations like choke points and pylons. Many times if the enemy only has 1-2 stationary defense buildings in their main base and their main army is relatively far away, a pack of Reapers can quickly infiltrate that base, destroy those defenses, and wreck an enemy economy, to still escape untouched by the time their army is able to react.