Shoebox is an alternative to iPhoto which lets you store and view a great number of pictures on your Mac.
Graced with an attractive interface, Shoebox is a very enjoyable application to use.
You can see all your different pictures in a thumbnail view and still get the hierarchical keyword structure at the top of the application window.
Shoebox also offers a number of different views including full screen to really enjoy your shots. Shoebox allows you to tag your pictures, which is probably the best way to keep track of all of them and can automatically import your snaps from iPhoto.
In terms of performance, Shoebox is definitely faster than iPhoto in processing and displaying pictures. Shoebox also offers Spotlight searches and advanced searching capabilities via multiple criteria, which is absolutely essential if you're dealing with a large photo library.
We also enjoyed using filters and creating private catalogs.
However, Shoebox lacks any option to print out books, calendars or stamps. Neither does it let you send your snaps to a photosharing site like Flickr, something which all photo viewers should offer by now.
It will let you burn discs or easily make backups though. Users have also complained about issues with slideshow view and the fact that Shoebox is limited to one computer, which is annoying if you need to upload your photos to two different Macs.
Despite not offering any printing options or photosharing online, Shoebox is a very fast photo viewer with a good keyword organization and tag management.