Yeah, it's really needed, and depending on who you ask you'll get different answers, and they are all probably acceptable.
Big caps are good at delivering high currents but may be slow to get there. Small caps are faster but run out of stored energy faster. Using both gets you closer to an ideal cap.
My mix is 10uF with 0.1uf or even 0.01 uf; typically I'll have one 10/0.1 pair at the regulator and toss in a 0.01 around every device I am concerned with.
While bypass caps are essential, it's not quite an exact science how you pick them. It's not uncommon to design in space on a PCB for an overkill of caps, then just populate the ones you think you really need after testing.
Big caps are good at delivering high currents but may be slow to get there. Small caps are faster but run out of stored energy faster. Using both gets you closer to an ideal cap.
My mix is 10uF with 0.1uf or even 0.01 uf; typically I'll have one 10/0.1 pair at the regulator and toss in a 0.01 around every device I am concerned with.
While bypass caps are essential, it's not quite an exact science how you pick them. It's not uncommon to design in space on a PCB for an overkill of caps, then just populate the ones you think you really need after testing.