I actually keep it installed because it's the easiest way of using Pentadactyl; I use it to compare behaviour with Tridactyl (e.g, looking for prior art for what a bind should be). As such I literally run it side by side with new Firefox. Honestly, it's just kind of slow. Mozilla have done a fantastic job in the last few years.

Have you tried Waterfox? I find it to be as good as FF 52

I did but a) 57+ is much quicker than 52; b) I couldn't actually get Vimperator to work, so I gave up and used Pale Moon for all my idea stealing needs.

Thanks!