I've used Locate32 and really liked it but then I tried File Tracer, just out of curiosity. Locate is a more refined program - far better GUI, way more customizable. I have to say though, when it comes to sheer power and low resource consumption File Tracer is God! Locate pushed my CPU to 40% and beyond whenever it indexed the drives. File Tracer just has you create an index the first time you run it and then does an extremely efficient job of realtime monitoring. If Locate32 gives "blazing fast" results, File Tracer gives near-instantaneous ones. The realtime indexing is so fast, if I search for "document" and open document.txt from the results, it shows up the resultant document.lnk from the 'Recent' folder 3 seconds after I run document.txt.
The most amazing part is, it seems to sitting at 0% CPU at most times. Locate consistently sat at 1.5% CPU in my case even when it was not doing a thing. As an additional plus File Tracer seems to have something like a condensed version of Filemon , I can comfortably view the realtime file system activity without having to filter out several apps like in Filemon.
Don't get me wrong, I love Locate32 but when something does its core job much more faster, much more effectively (no indexing required) AND uses a fraction of the resources you gotta give it its due.