Yesterday I downloaded and installed the Google Desktop search for Linux on my openSUSE 10.2 system. So far, it seems great, I don't have anything bad to say about it. It doesn't produce any noticeable CPU load while indexing your documents, and it returns desktop search results quickly, in the familiar Google format.
I use the GNOME desktop for Linux, which comes with the "beagle" desktop search application. Beagle is widely integrated into GNOME applications, but unfortunately the version that comes with openSUSE 10.2 has a known bug where it loads the CPU to 100% (apparently due to rescanning of folders that it has already indexed). In principle, I could have downloaded and installed a later version of beagle, but I probably would also have had to download updated versions of all the beagle integration packages. It was easier to just get rid of beagle and install Google Desktop.
Google Desktop integrates most closely with Firefox, but you can get it to return results in a different browser by changing your GNOME browser preference in the "Preferred Applications" settings. I have my system set up so that Google Desktop now gives me my results in Opera instead. I also configured Google Desktop to ignore my Opera e-mail folders, since Opera's own built-in search is extremely fast, so I don't need Google Desktop for that.
So far, so good.