That does work, yes, but you still need to sync trunk changes to your branch, of course. The nice thing is that it does not require you to keep track of revisions that have already been merged. Instead, whenever you’re bored for a moment, you do
svn merge https://…/trunk
in a clean branch working copy, and it will figure out what revisions to sync over.
Once that is done, you can to the –reintegrate merge in a clean trunk copy to have your branch merged back.

That’s an SVN 1.5 feature, and I’m hearing there are still a couple of problems with it when it comes to moving of files etc. Most people so far use, which essentially does the same thing. I always merge by hand, as I don’t find it particularly difficult, but I guess it’s all a matter of taste :)