So the Easel theme's CSS3 gradients don't work on Opera, I have resolved this problem and I would like to see it resolved in Easel itself.
First, update to the latest version of Opera, which supports CSS3 gradients. Then, by #menubar-wrapper inside style-default.css, under background: moz-linear-gradient, paste this:
That will make one of the gradients work.
The second one (for selection of menu items) is down there, just find the second moz-linear-gradient and paste this under that:
Your Easel powered site now works properly on Opera!
Still figuring out how to make text-shadows work properly, though.