If you are serious about managing your images, consider a dedicated catalogue program such as Espression Media Pro or Extensis Portfolio. They are a huge step up from browsers which do not maintain data, and need to create new thumbnails every time you open them. You can enter your metadata, & key words, and create catalogue sets - which make finding your images a BREEZE! I work my images in LightRoom (sorry Apple), finish them in Photoshop, and then manage them in Expression Media. Lightroom has very good cataloguing properties, but on my G5 is a bit slow. A Super resource for the serious shooter: The DAM Book, by Peter Krough - O'Reilly Media.
Google, Please Bring Picasa to the Mac