Spaces in OS X

Tried out Spaces today. This is basically the equivalent of the Linux multiple desktops.
I found it certainly useful but am dissappointed that on reboot you lose all of your carefully arranged spaces and have to set them up again.
One advantage is that chnaging spaces to get to another "desktop", is almost instantaneous so it's a lot faster than, say, launching a browser from the dock.
It's worth persisting with to get a better picture of its usefulness.