For the people who use Alfred (http://www.alfredapp.com/), I'm curious to know Alfred's advantages over the native Spotlight (which IMO works fairly well) or other similar apps like Found (https://www.foundapp.com/) or Quicksilver (http://qsapp.com/download.php)?
Oh and to add my two cents to the OP's question:
HyperDock (http://hyperdock.bahoom.com/): Windows 7 functionality to preview individual windows