Sergey,
I've found most processor resets have enough
built in capacitance that a simple schmitt provides enough
hysteresis to sufficiently debounce a switch input if it's even
needed at all. But I've found many situations where the reset
needs to be held for a set sequence time while the power supply
is stabilizing from power-on in-rush and the simplest solution
I've found - both in $$ and BoM count is a Microchip MCP130.
They tend to work well and are available in a variety of
threshold voltages and in both SMT (SOT23) and through-hole
(TO92) packages. And I eliminate the need for the explicit
debounce if I tie the switch to the enable on the LDO or
switcher and put the MCP130 on the output side.
I've also used ATX PicoPSUs in designs and
added a Maxim MAX16054 specifically to turn a simple SPST
push-button into a ATX power-on toggle. However they and some
of the other parts like it from Maxim are not available in a
through-hole package - only SOT23-6.
Hope this helps.
-Alan