Your question is formulated wrongly but I guess I know what you want: what's the lowest frequency needed by a laptop CPU so that it runs well for "average use".
Nobody can really tell you that because "average use" for me might mean a totally different thing than what it means for you; also my picky-ness might be greater than yours (or lower); the final point is that a CPU alone can't drive a smooth system -> a system with 2 Gb of RAM or with 4 gb of ram @ 1033 MHz or with a 5400 rpm HDD will run a lot slower than one with 8 Gb RAM @ 1600 Mhz and a 256/ 512 Gb SSD.
Let's say that it's acceptable (but not extremely smooth and by far not wow) a laptop with 7200 RPM, 8 GB of ram @ 1333 MHz (or more), any quad-core CPU that's the latest possible generation that's running @ 2 GHz.