since i'm a folder hierarchy organization kind of cat, picture switcher is still the best wallpaper switcher for me.
while others require you to spend some time organizing your wallpapers inside the app itself (smart folders collections) or depend on an internet connection to fecth online wallpapers, picture switcher let you choose one more base folders from your hard drive and present them in the menubar and i mean, the full hierarchy, so you're not limited to a flat folder scheme.
since i organize my wallpapers by mood or theme, this is very welcome.
it also allows to choose a time interval from seconds to days (maybe even months, can't remember well right now) for your picture rotation, transition effects, image filtering effects (sepia, perspective, etc.), has a built-in image viewer with cute thumbnails, multi-monitor support and all configured through the menubar (no need to go into deep hidden preferences).
more, it supports global hotkeys to change wallpaper on demand, change the time interval an other options.
my only 4 wish list/bug fix requests which were never answered by the dev, since the latest update is from 2007 were:
1. new hotkey to change monitor selection (currently you can only change the focused monitor on the menubar) so you could change to the next wallpaper, on demand, on both monitors, without using the mouse.
2. refresh the menubar folder hierarchy automatically when adding/trashing images in finder/path finder. i think the only way is to disable and enable the added folder again or quit and relaunch picture switcher.
3. when wallpapers reside on an external drive and it's disconnected/ejected, when you connect it back, it should enable automatically the base folders you added. right now they stay disabled until you enable them again in 'folders' in the menubar.
4. correct a bug that when running an app which changes screen resolution (a game, for instance) and exiting, the wallpaper gets cut off when swithicng back to the default resolution (the bottom half remains with the last wallpaper and newly changed wallpapers only update on the top half of the screen. quitting and relaunching picture switcher fixes it).