I was never actually bothered by this dialog, but this morning I was imagining what a newcomer to IDEA would think about it -- there's too much information in a badly structured and presented way. Here are a couple of things that should make it more usable:
1) Organize plugins in category trees. Plugins already have categories associated with them, IDEA just need to show it in a more elegant way. How about a tree-based control, where the user can expand/collapse each individual category?
2) Show only the plugin name and versions (installed/available). There are currently 8 columns in the plugin table, and most of this information isn't that important. How about showing just the name and versions, and moving all the other info to the bottom panel, together with the full description and change notes?
I'll try to design a mock in my lunch time, and if it looks good, I'll open an issue for it. In the meanwhile, any comments?