The super speed only works for you, but not the symbiots in your body, like your gut bacteria. The increased metabolism combined with the still normal speed gut microbiota causes extreme diarrhea, so everytime you use it, you shit your pants violently.

you gain super speed, but cognition remains the same. your day is a constant struggle to plan out a meticulous series of moves, otherwise you'll destroy your house trying to walk downstairs. this becomes particularly vexing for those middle-of-the-night strolls to the pisser. perhaps if you survive long enough you can adapt to the situation, but that seems unlikely.

You have to eat enough calories to keep up with it, and while your body is stronger, you'll still wear out and likely need all your joints replaced within a decade.

your body is not more resistant to high g-force

I like to imagine that this is what it's actually like for The Flash, or Quicksilver or another speedster:

Sure, you can move super fast, but to do that, your thinking also has to speed up to handle that fast movement. So, it's more like everything else in the universe slows down except you. Now, it's still an amazing power, but think about those times when The Flash uses his super speed to build a brick wall nearly instantly, or to read every book in the library in the blink of an eye.

To you, building that brick wall takes what feels like a week. You're running at what feels like 30 km/h to get a handful of bricks. It feels like it takes you about 20 minutes to get to the place with the bricks. You run them back to the place you're building the wall, you put them into the wall. Then you run another 20 minutes to get the next load of bricks. While you're doing this boring wall building, you can't chat with anybody, you can't listen to a podcast, you're just stuck doing manual labour for what feels like a week without any distractions or entertainment.

If you speed-read every book in a library, that feels like it takes a month. Hopefully you like reading dry reference books, or whatever it is you're reading, because that's all you get to do for however long it takes. Someone watching you might see you flipping through the pages in fractions of a second. But, to you, it still feels like it takes 2 minutes or so per page, and that's if the material isn't difficult to understand.

Maybe super speed needs to come with super autism so that you get really engaged in these tasks and don't mind sinking what feels like days, weeks or months into one monotonous thing.

You are still vulnerable to friction.

Doesn't come with super damage resistance or super maneuverability. You cannot instantly turn or stop, and one mistake will lead to you crashing into something to death.