Progress gauges slowing things down
For some reason, progress gauge takes a very long time to come up and
disappear. It seems as if there was a (sleep-for 1) hidden in the
code.
To repeat, try opening a very small .c file with progress gauges. The
delay is very noticeable and quite annoying. I often hit this when
replying to messages in Gnus (Gnus "message" mode uses font-lock for
highlighting.)