I use Firefox exclusively, and it downloads just fine. A couple things: Generally don't rely on website buttons, take the back door.
I was surprised the evo has become a site where you can literally right-click on a video frame and "Save as..."
When it's not that f'in obvious, the following works 60% of the time, including on Spankbang (it has been for years now).
In FIREFOX, open up a video. Hit ctrl-i, then the Media tab, then reverse sort media type so the video is at the top and easier to find.
If it the Video isn't grayed out, you can download it fine. No need for creepy, sketchy download extensions that are probably spying on you and monetizing your traffic.
If the video is grayed out, that means its globbed, and it is possible to get globbed videos with some extensions, but I usually look for the thing elsewhere.