I found NotLight to work brilliantly. It is instantaneous and really addresses all of the flaws of Spotlight. But...
C'mon. Zero instructions. And while eventually simplistic, the default is not common sense. So if you do a search, you get nothing, because you have to select the "Word-Based" checkbox to tell it you are looking for a word (in a file title, for example.) Similarly, the default is case sensitive. Looking for a capitalized name in an email file?; you must check case insensitive or make your entry capitalized.
A three paragraph ReadMe document would resolve all of this and probably resolve the reviews from people who can't make it work.
Complaint: Previous checkboxes do not remain checked, nor is there a preference selection to make this the default. 95% of my searches will be word-based and case-insensitive; I would rather not have to spend the half second to reselect these boxes each time I use NotLIght. My guess is that the author will put this in soon, as this is a .5 release. This really is a good product.