For a CRT, yes it does matter. Read Cucumba's post about why.
For an LCD, it doesn't matter as much. LCDs don't flicker, they just change color/brightness. But, having a higher refresh rate on an LCD can smooth out things if the LCD can keep up with the demand of change. A slow LCD may only be able to change the color of its pixels 55 times a second, so anything over 60hz wouldn't be noticed. If your LCD can change the color of its pixels 75 times a second, then 60hz-75hz would be noticable.