Some of them do better than 1/2 Impact (some ignore it completely).
The downside to them -- to me, at least -- is that none of them are really appropriate for a stone-cold-pro type of shadowrunner. Thunderous cracks when you hit someone in melee, flashes of light, blasts of fire, stuff like that? It's all awesome, but a little inappropriate for your bog-standard "sneak in, fight quietly if you can, sneak out" type of stuff. They're a little flashier than I like my average shadowrunner to be, so I've never really played with any of 'em very much. They're all (potentially) pretty danged effective in combat, but never quite feel right to me.