Thanks to a user report, I just found out the the recent v5 versions of rsyslog have hit and exceeded the one million message per second (mps) mark! In my lab, with commodity hardware I reach around 500,000 mps. In practice this seems to be at least doubled :)
This strengthens even further that rsyslog is the syslogd of choice for demanding high-traffic environments :)
The full report is here:
http://kb.monitorware.com/000-000-character-messages-sec-with-rsyslog-t10740.html