This came through as a question on reddit with 87 net votes, showing a screenshot of Chrome's "Search Tabs" feature (in the tab strip).
People pointed out that you can search tab titles via the address bar using the % restriction token. However, this is a bit of a multi-step process, unlike the same feature in Chrome, which allows people to do a Ctrl-shift-a and begin typing for the tab vs. the Firefox feature, which requires people to do Ctrl-l then type % space and begin typing the tab title.
Ideally, there would be a keyboard shortcut that would focus the address bar with the restriction token already populated.