You can also do a server-side svn copy to create a branch of trunk (which is relatively instantaneous), then use svn switch to selectively swap out the directories in your working copy relevant to your change. I usually wrap this up in small bash scripts at the root directory that "toggle" the switches. I call it "poor man's dvcs."

Have you tried git-svn? The initial checkout can take a while, but it gives you many of the features of git, while still using svn.