I've added some new functionality. You can now quickly add multiple boards to your comparison from the filter page. You no longer have to go to every board's detail page and add the boards one by one. You can select all boards you want to compare and then go to the compare page.
If it doesn't work, you might need to force reload the site (ctrl + F5) to download the newest code :)
Another small improvement I added is that when opening/closing filter sections the page no longer jumps to the top. I have no idea how long it did that, but I only noticed a couple of days ago (maybe I broke something in a previous update, not sure). In any case, it annoyed the hell out of me and it's fixed now.