I have Kent, but I am in process of building a DIY kalk drip system, so have'nt used it. Got it for free and have heard good things. Probably not much help, but figured you needed da bump.
I'd probably give pickling lime a try too but I've always heard it wears the impeller really fast on kalkreactors that use a powerhead for mixing (like mine).
ESV has a reputation for not effecting the impellers, so I've stuck with it...(and had no impeller problems).