One thing I've noticed since I started using Sideberry extension (a different/better take on Tree Style Tabs) is that after a day or two, the whole tab panel I separated specifically for HN tends to accumulate 100+ tabs. Having them laid out vertically in tiny font makes this apparent in a way that the regular tab bar doesn't.
Fortunately, I also habituated the simple behavior of "If I realize I have a lot of HN tabs open, right-click and close the entire pane". That's how I know I'm clocking about 100 tabs per two days on HN alone.
Also, Sideberry changed my tab hoarding habit in a way that still results in keeping hundreds of tabs, but using them in much more sensible way. I keep them arranged in trees stemming from topical groups on high-level panels, and trim or kill as they're no longer useful. Most of those tabs are unloaded anyway, but the interface works as excellent short-term (days to weeks, sometimes a few months) bookmarking system - and I don't lose tabs anymore (as in knowing the tab is there somewhere, but not being able to find it in the vast sea of other tabs).
Except for the annoying interaction (I think) with "open new tabs next to current tab", which causes Sideberry to somehow leave behind lots of stupid empty tabs named after the page the real new tab had. I deal with it, but it's annoying.
Oh, I'm yet to hit that problem. My current annoyance is that sometimes it gets confused after Firefox restarts, and I end up with a flat dump of tabs + an unending spam of those tiny warning popups at the bottom of its UI. The few times that happened, I ended up restarting Firefox again to stop the warnings, and then rearranging the flat list of tabs into groups and panels I want them to be in. Fortunately, it's not that big of a chore.
I switched to Sidebery a couple of months ago, and I find that it's somewhat better at restoring trees (though that could just be luck). I feel it's a bit more responsive, but these days I trim my tabs a bit more aggresive than I used to so my TST memories are somewhat biased.
I was surprised at how decent it converted TST tabs, but I can't remember how low my bar was; maybe try a new profile?
One thing I'm finding really nice in Sidebery though that TST can't do, is that I can create a parent node that is not attached to a specific page (via grouping).
Panels I'm undecided on. They seem useful, but they also seem like a bandaid over window management tools. One problem I'm having is that they don't restore, and all the tabs go back to the main panel. That may be some setting I toggled though.
Honestly, I don't remember. A year ago when I was considering going back to vertical tabs, I read a bunch of discussion thread and articles, and got the impression Sideberry might be better. Tried it, and it resonates with me - unlike TST, which I tried and quickly abandoned several times over the year.
Can't really point to any concrete issue, other than I have a distinct feeling Sideberry is much faster/lighter, and feels more like part of Firefox vs. some bunch of JS faking an UI on top of it. Sorry I can't give you a more objective comparison. I did find this though:
Fortunately, I also habituated the simple behavior of "If I realize I have a lot of HN tabs open, right-click and close the entire pane". That's how I know I'm clocking about 100 tabs per two days on HN alone.
Also, Sideberry changed my tab hoarding habit in a way that still results in keeping hundreds of tabs, but using them in much more sensible way. I keep them arranged in trees stemming from topical groups on high-level panels, and trim or kill as they're no longer useful. Most of those tabs are unloaded anyway, but the interface works as excellent short-term (days to weeks, sometimes a few months) bookmarking system - and I don't lose tabs anymore (as in knowing the tab is there somewhere, but not being able to find it in the vast sea of other tabs).