Wouldn't it be better to base the release of a clean check out to a temp directory, so you're 100% certain it contains what's in the repo and nothing else?

I agree. Additionally, I would do a svn copy to tag the release.

When using cvs it could look like this:

REV=MyApp-0-2-1-b
mkdir -p /tmp/$REV
cd /tmp/$REV
cvs export -r $REV MyApp
tar -cvf $REV.tar MyApp
bzip2 $REV.tar
rm -rf MyApp
[download]

I guess a similar thing is possible for subversion also.