F-Spot is a relatively clumsy photo-manager. Some issues are:
1) It completely ignores my organization of photos into folders and imposes its own schemes and tries to make a duplicate copy of all photos to "import" it into the F-spot collection. Why can't the organizer respect the organization that the user already has and build up on that?
2) Image rendering is noticably slower than gThumb. Each image takes some time to fully rendered/are fuzzy.
3) In full screen mode, I'm forced to have some form of transition effect between images and the slideshow is jittery, including the fullscreen toolbar.
4) When I delete pics from outside (say, Nautilus), it doesnt autoremove pics from db the next time I run it.
5) F-spot manager does not open when image is opened from Nautilus.

gThumb is so much better in all these aspects. Moreover, you can also choose to work with your collection in Nautilus if you feel like, without having to open the photo manager every time you need to touch your photos.