F-Spot is a killer app, if I've ever used one. I finally got around to importing and tagging all of my photos--it was a cinch--and I enjoy using it. It is really just a well designed chunk of code.
The amazing thing about it is how the interface is just right, learnable yet usable. Also, it scales real well: It does not flinch one bit at all my photos.
Leaving tomorrow in a jet plane for Australia. Not looking forward to that flight whatsoever.