@khahan In part I agree, but keep in mind that in a prison list, 2 of those 4 abilites are worthless.
"Spells you cast cost 1 less to cast" doesn't REALLY matter because you're already casting your most expensive spell through spheres anyway.
"Creatures you control get +1/+1" hardly matters in a prison shell.
Shutting down PWs (Fayden specially) and drawing cards is probably enough though. One of the reasons Coercive Portal is bad against control is because it can easily be stolen and ruin your game completely.