Yes, there are lot of threads on these fora on problems relating with installing/updating EN if you google for this string "Evernote was already installed by another user. Only one per-user installation is supported."
Revo was totally useless since it was "hidden" installation of EN. That is, it was uninstalled but still was present in the system for some reasons. You can't see it in the Program Uninstall Control Panel applet, you can't upgrade, you can't uninstall.
What was really useful is MS The Program Install and Uninstall troubleshooter. Provided with GUID (taken from %TMP%/Evernote_setup_log.txt) it can uninstall everything, even hidden.
After some manipulations I was able to run old instance of EN. Then choose Update from menu, EN downloaded last 6.25 .MSI file (not .EXE which can't be installed due this cryptic error). Et woo a la that was it upgraded/installed itself sucessfully