I'm an avid Vimium user so I'd love if it got some attention, probably my biggest pain point in switching from Firefox to Orion. I could even sponsor this issue; I'd happily pay to be able to use it since I use it for accessibility reasons.
One bug that hasn't been mentioned is that it seems like some options simply don't get applied even though they do get saved, but this is a bit inconsistent and sometimes the options do get applied for a while only to stop working later. Eg. changing "Characters used for link hints" mainly doesn't do anything for me, and no matter what I put in there it uses the defaults. Also changing "CSS for Vimium UI" doesn't seem to do anything most of the time (except sometimes it does, so one of my test profiles has massive red link hint boxes which I haven't been able to change back to the default yet. I'm not sure what I did differently.) It seems like often even if eg. the link hint setting actually does get applied when I change it, if I reload the page it'll go back to the defaults again.
In general saving settings usually takes at least two presses of the "Save Changes" button before it indicates the changes were saved by changing the text to "Saved" and greying out. The Vimium logging URL (moz-extension://d7742d87-e61d-4b78-b8a1-b469842139fa/pages/logging.html for me but I have no idea if that UUID is just local or not) unfortunately shows no output, and the javascript console on that page has Failed to load resource: The operation couldn’t be completed. (Orion_RC.SchemeHandlerError error 2.)
(same error in the main Orion version, just without the _RC
) .
This was tested with the Firefox Vimium-FF plugin (I'm relatively sure the Chrome version has the same issues, or at least I remember testing it out a while ago and finding no real difference at least at that point) and the latest Orion RC (Orion 0.99.125-rc (WebKit 616.1.22)) and latest main version (0.99.125-beta (WebKit 616.1.22)).