Yep. About as much as you’d expect going from an AA to a 14500 and about in line with other lights. All 3 modes work fine but as expected, the gap between “low” (which is really medium) and high narrows. I keep an Eneloop in mine, but I like to be thorough so I always try a li-ion in any new flashlight. My old T10 (which is now called Saber) which is a twisty doesn’t work right on medium with a 14500. That and a couple other reasons make me think the T10S uses a new circuit.
I do know that I’m hard on my equipment and the clips, too, but I’ve never had a clip like this one bend so easily on any other brand of light like EagleTac, Nitecore, etc. I just think it’s not as rigid as it should be. One of these days this week I’m going to dig through a few sites like DX and FT and see if I can find a good aftermarket clip for my T10S.