There are things to like about the new addons page, and just as many not to like. For instance, this major annoyance: when disabling an addon, it does not stay right there and indicate that it’s been disabled like with the old interface. Instead, the disabled addon disappears; it is then found in the Disabled section.
With 55 addons, all the paging up and down is a big hassle compared to how it used to work. Yes, I know I can disable ‘extensions.htmlaboutaddons.enabled’ but I’m sure that option will be deprecated soon.
If you are tempted to try a style hack in a userContent.css file, here is an example of a two-column extensions list, Enabled on the left, Disabled on the right. (Widths are hard-coded, I couldn’t figure out a good way to make the layout responsive.)
Thanks a lot, @jscher2000. I like it; tweaked it a good deal to fit the margins/compact, etc. Still missing the one-click-to-disable/enable, but this is an improvement.