I tried to use WPMU DEV Dashboard on a Chrome and Firefox browser. They both showed active but only one shows on the admin page.
When I deactivate and activate it shows up on that browser but is removed from the second one. So you can't jump from browser to browser, as in checking that each page loads and looks the same no matter what browser your using. This to me is bad. You should be able to have this plugin show on each and every browser you are using.