I bought a DeSantis ankle holster about 20 years ago and still use it and it is the most comfortable ankle holster I ever wore. I could wear it for 24 hours and there was no hint of being uncomfortable.
I'll second the Desantis holster, so far, of the half dozen or so I've tried, its been the most comfortable holster of this type I've used.
I use one occasionally, depending on need. If you wear the right pants and practice a little, the gun is not hard to get to, and you might be surprised, but you can do it pretty quick. I practice both dropping to one knee, and on one leg, staying standing. Its great if your in the car a lot.
Depending on what you do for a living, something you might want to consider is, your placing your gun in a bad place as far as dirt and water go.
Its also somewhat subject to abuse, and you also need to pay attention when your seated in public and how you place your legs. Next to shoulder holsters, its probably the second easiest to spot.
As an alternative, have you considered Smart Carry. Since I discovered it, I've used mine daily. It works great with smaller pistols/revolvers, and you forget you have it on. Its got a waterproof backing and your gun is well protected. You'll be amazed at how well it works at concealing your gun and its not hard at all to get to, even sitting.