0% in the beginning. Low forever after.

I sometimes consider going with low even in the beginning. 0% is no longer as obvious as it used to be in some betas.

I start at no taxes and live for dozens of turns on looting defeated monsters and doing the occasional quest.  When I finally run down to under 75 gold, I'll switch to low.  Later in the game, I eventually notice that I have 20,000+ gold in the bank and at least consider going back to no taxes, but usually don't, purely because I don't want my markets and other gold-producing city improvements to go to waste.

My current game, I'm playing Stormworld's Undead faction, whose default sov is Wealthy and there are racial abilities that result in unit wages eventually turning into an additional source of income independent of taxes.  I could be wrong, but I have a feeling I'll stay at "no taxes" the entire game this time.

Agreed.  I leave it at low the whole game.  Seems like this is missing something it could be adding to the game.

Start out at no tax until the gildar income becomes important , and I run it low until what I consider beyond lategame, when my cities can support medium tax with only a maximum of 10% unrest.

Yes it could use a little something, mostly I don't like how cities have several items that reduce unrest, so the tax is only really there to increase when you reduced unrest by enough amounts.
I think it would be way healthier to have a system without unrest reducing buildings, well meaby except a tiny amount, like the "Tower of Dominion", and meaby some specific level-up buildings.
That said as long as it affects research it will remain on no or low taxes.

Sincerely
~ Kongdej

I would get rid of the tax slider altogether.

Unrest should affect gildar income like it affects research and production.  Then adjust unrest rates such that it's almost impossible to get unrest = 0 (I also like the unrest per city idea personally.)  Then rebalance research and production rates if necessary.

Well, even if they fixed the messed up numbers on the tax rates (Sean did this in his own mod, so I DID try it out this way), as long as the unrest affect the research just to give me a meagre piece of gildar, I will always try to keep unrest on a minimum, since better Research > Gildar, especially in the current rates you can gain it.

I do like the idea behind taxes, but currently they don't work, I always liked trying to have some of my empires produce stuff slowly, but being good at rushing the important stuff wherever I feel its needed, this also helps me get my new cities built faster, and I can ignore the amount of materials at each specific place, but due to the low gildar income and rather high gold cost for rushing, this is a a tactic I can't make work in FE...

Sincerely
~ Kongdej