When you are sitting on a particular addon's page, you usually have a little window that says:
Addon Packs Containing This...
Now if you start scrolling while the page is still loading, you'll see in this section a huge selection of UIs that contain it. But once the page is finished loading you only see the first 5. There is nothing wrong with this except there is no way of getting to the rest of the packs past the first 5. There is no "More" or "Show More" button on that window that would send you to all the rest of the compilations that contain the addon though clearly there are more that contain it.
You can say, well you can go back to the searchbox and type in addon name, and among the search results, you can pick Addon Packs instead of Addons and get a bigger list. The problem is, this list is also limited to only one page though there will be a number listed next to addon packs (like 50 or 100), that shows there are clearly more than just shown on that first page. The "See Details" button on the Addon Packs category is also not working for me, though when I select Addon instead, "See Details" works just fine.
What's more, again there is no tooltip info that you can quickly browse through the compilations without loading each one individually, and there is no option for thumbview viewing the way there is when you're linking on the addon page in that "Addon Packs Containing This" window.
I hope some of these issues are addressed as they aren't major problems. They would just make searching through addon packs a lot easier.