If you're willing to go to a certain amount of trouble, you can assign permanent keyboard shortcuts to each of your bookmarks bar (non-folder) bookmarks via System Preferences -> Keyboard -> Keyboard Shortcuts -> Application Shortcuts. Just type the name of the bookmark in the Menu Title field.
Caveat #1: It seems that ⌘-1, ⌘-2, etc. are reserved for the first ten (non-folder) items in the bookmarks bar; these commands are not overridden by reassignment to specific entries. But when I used ^⌘-1, ^⌘-2, etc., they worked as expected.
Caveat #2: Earlier versions of Safari apparently require that the bookmarks bar menu in which the commands appear (Bookmarks -> Bookmarks Bar) be displayed once each time Safari is launched before these user-assigned shortcuts are functional. The
blog post where I discovered this solution is over two years old; the bug discussed therein appears not to be present in Safari 6.
Edit: I was wrong about Safari 6; the same bug applies. The menu must be displayed following a relaunch before the commands become functional. In any case, not too much of a penalty for those whose uptimes are days or weeks at a time. Overcoming the ⌘-
n muscle memory is probably the greater issue...