I think that the default value of 20 items per page on the list table screens (posts, pages, media, users, CPTs, etc) is too low, and makes the user experience frustrating. It's annoying that I have to click over and over, and each time load a whole new page, just to browse for things that could have easily been displayed on the first page load.
I can manually set a higher default value via the Screen Options dialog, but I have to do that for each screen, on every site I build.
I can search instead of browse, but that still results in another page load, and then I have to dig through the results, where the sort order isn't as intuitive as it is when browsing.
I think somewhere between 40 and 75 would be a much more reasonable default value, and it'd also be nice to make the default value filterable, so that a plugin could easily change it site-wide if people want to raise or lower it.
A different alternative would be to use an infinite scroll, but I think that from a UX standpoint, those are even worse than pagination.