Being a (very) lazy software guy, I'd rather write an entire library just to debounce a pin than to figure the resistor or capacitor values to use 
but I try to keep the code at least debuggable. Interrupts are somewhat fascinating, but they're the gate to the hell of heisenbugs. So I try to avoid them as much as possible. Netsted ISRs ? Maybe when I'll start my own aRTOSuino 