Tab takes a long time to open.

[JAStanton]

Most likely due to the fact that there are A LOT of elements on this page, just thought I'd check to see if anyone else was seeing this behavior. I'm not sure what a good solution would be except for maybe pagination / lazy loading.
Images can also be a big pain to rendering engine. Or start with sections collapsed. It seems when I collapse all and tab back and forth it seems to be regular speed.
Or crazy idea here, iframes, but all the sections into iframes. Don't look at me like I'm crazy iframes have a unique behavior where upon the root has to relyaout it just recalcs the iframe's position and not the iframe's contents / child nodes. Think about that one for a while ;) this could theoretically be big perf win. I never tried it myself but theoretically!!

[benogle]

Yeah, it needs optimization. It's evaling all the space-pen stuff on the page, and doing a bunch of other junk that is likely slow.

If you feel like digging in, I would start by profiling it and figure out where the slowest parts are. That would be awesome. There is probably some really low hanging fruit.

[Azeirah]

I saw another package using an iframe to render html in, instead of using spacepen where most of the performance issues probably come from, we could rewrite the styleguide in html, and put the html inside of the iframe.

That is, if spacepen is slowing this down so much, otherwise it won't do much.