For a check done exactly the same way as the disc's built-in
mediacheck, except without having to reboot, one can install the
anaconda-runtime package from Core, and then run the
/usr/lib/anaconda-runtime/checkisomd5 command. The page
http://www.troubleshooters.com/linux/coasterless.htm
also provides a script to automatically read off the ISO from the CD or
DVD, which allows checking the ISO's SHA1SUM directly, and also how to
burn a CD using padding so as to sidestep the linux read-ahead bug.
From some experimenting burning the FC6 DVD ISO, I've found that the
same bug affects the reading of DVDs, and that it's necessary to add the
same type of padding in this case. Since growisofs doesn't allow adding
padding after the ISO (it passes -pad through to mkisofs, which puts
padding _inside_ the ISO itself, which is different, and anyway not
usable when trying to burn a downloaded ISO), one must use cdrecord.
I've done this successfully in exactly the same way as with a CD except
that one doesn't use the blank option. The resulting discs avoid the
read-ahead bug even though growisofs-burned ones don't.
