hell yes we need this!
at the moment i use an Redstonetorch to indicate if the reactor is active or not (as i'm a big fan of vanilla redstone clocks and high mark reactors)
welcome to the forums, i generally stick to Vanilla Redstone as well but sometimes, especially on SMP, it starts to cause issues with alot of redstone use. i agree though, we do need this and it would be nice to have this and the Thermometer/Control Block added. also that reminds me. Alblaka, if you read this, could you make the Nuclear Control block make an Emergency Evacuation siren when it reaches 85%+?