It's pretty nice but... Rated 3 out of 5 stars
There is a bug I found when using stumble upon. If I middle click the stumble upon button to open a stumble in a new tab and I open a link on the stumbled page in a new tab the history will go back to the page I originally clicked the stumble upon button at rather than the page I came from. It'd be really rad if this could be fixed.
I'll continue to use this just because it works most of the time, I just hope it's made to be a bit more compatible with other plugins.