So, how do you make things transparent without using opacity?
I am the one who made the theme, and it is my first. I have zero background in this so bare with me I'm learning.
However, aside from the one or two in this thread, I have not heard any complaints about speed or lack of.
Well it looks nice regardless. Most first time themes I've seen almost look like a rainbow. But your color contrast flows perfectly...
Anyway, your opacity is barely the issue - at least for new computers. I'm running a 4-5 year old machine and it renders the site perfectly once I disable your background image. The only way to avoid the lag is to opt out the background image (and you have 2 set).
My suggestion to you is if you don't want people to complain, instead of setting the background image as a fixed position, try doing a repeat-y and see how that looks. Also, you have 2 background images set on the page.
One on your <body id="ipboard_body"> tag and then another one your <div id="content"> tag.