I don't need extra keyboard shortcuts and am not sure how they would help. I already have Vimium for keyboard shortcuts. My tabs are just naturally organized into logical groupings, so I can visually scan for what I want very fast. Searching is nice when you can immediately think of the appropriate search terms but it's not a replacement for a clean visual arrangement of my tabs. Another very simple benefit is that I can read the tab title text easily even with lots of tabs, something that breaks down very fast with horizontally arranged tabs.

It helps that at this point I have a lot of subconscious habits about how I arrange tabs automatically. For instance, when browsing something like HN from the front page, if a link interests me I'll middle-click the comments link first, opening it in a sub-tab. If I'm interested in the article as well, then from the comments sub-tab I'll middle-click the article link, generating a sub-sub-tab. I don't even think about this; it's just how I've browsed sites like HN for a long time at this point. I end up with a nice little structured recreation of whatever part of the homepage I'm interested in at that moment. Then, if I don't want to worry about HN right now, I just collapse the entire tree and come back to it when I want a break.