SS1 was widely criticized for being overpowered, the rate that it could spawn mobs at and that they worked even when the player was up to 100 blocks away. It's a no-win situation, I feel sorry for anyone who sticks their neck out by releasing and updating a mod.
True. But the only criticism against it is the material required vs it's' function.
Yes, you can spawn them in the overworld but the requirement of it needing the essence which can only be gotten by breaking spawners means you are pretty limited by it.
Compared to how DC handles it by making you grind the mobs for a chance at chunks, which you would need a lot of, to craft a regular spawner.
But adheres to vanilla spawning mechanics of requiring a player near it, so there really isn't much of an advantage to SS2 since one could just place a spawner (blaze, zombie pigmen or wither skeleton) in the nether near their nether portal.
Item sorting could always be sent transdimensional back to base by using either enderstorage or tesseracts.
All in all, all I'm not pleased with the cost to effect ratio. But of course, if he adds in upgrades later on (wouldn't mind the cost of more essences required if it's not too outrageous) to improve the capability of the spawners, I would probably change my tune.