A --no-ff merge also makes reverting a change from master easier because there is just one commit. You don't need to dig through the log to find the first commit from the merged branch fast-forwarded onto master.
using "git revert <merge_commit>" is very nasty[1]. using 'git reset <before_bad_merge> is less so.
[1]http://kernel.org/pub/software/scm/git/docs/howto/revert-a-f...