I believe RapidSVN has you use bookmarks (which are accessed one at a time.)
Checkout is the command you use to create a new local copy from the repository. You only use it once.
Update is the command for getting the latest changes from the repository into your local working copy. First select the bookmark. Then you can use the toolbar icon (has a green arrow in the screenshot I've got), use the hotkey Ctrl-U or use the menu item Modify -> Update.
If you're just wanting the fastest way to keep updated and aren't afraid of the commandline use the official subversion executables.
After a deluge of problems with both RapidSVN and Tortoise, I too have gone the way of the command line and uninstalled the two offending programs.
I agree also:
I believe a (very) short explanation of how to use the commandline dealie belongs in the "what is the svn" wiki
The link to the install file here is great...also a note about use of ~1 to shorten folder names and such (basic command line usage info that we should probably already know :X, basically write it like you would for say, my mother!)