I've recently encountered one 805x circuit with a 1000 uF cap on its Vcc rail, that had unidentified problems which were initially called "reset" issues. By removing the 1000 uF electrolytic cap, I made the problem "disappear" though I'm not yet sure why. Some circuit designers believe that one can't have too much capacitance on Vcc, though I view it as being like "You can't have too much garlic." The circuit in question now has one 100 nF cap on each IC and one 10 uF tanatalum at the power connector.

If you're worried about the Vcc-to-Gnd capacitance damaging your regulator, you should consider putting a diode in reverse bias (from output to input) on your regulator, so that if the power goes down the capacitance on Vcc won't reverse bias the regulator. Problems can occur when repeatedly switching power on and off, particularly if there's a bleed resistor on the unregulated power supply's capacitor, as the resistor will discharge that cap once power is turned off, while the Vcc-to-Gnd caps may discharge more slowly, though that can occur any time power is turned off.

This is true for LDO's as well as for the "normal" 7805-types. A simple 1N4001 is probably adequate for this purpose.

As for switchers ... I doubt you'll ever find one that has sufficiently low output noise/ripple to warrant their use without a downstream linear regulator and considerable filtering on both sides of that in order to provide sufficient line and load regulation.

RE