I've had a standing desk since 2013. I have no ragrets.
Standing gives you more energy, drains you less, BUT you can't stand all day. You need a stool to lean against, to sit on, to comfort your new standing position when your legs get tired.
I do a rough combo of 50% standing, 30% leaning, and 20% sitting. To switch things up, you need a stool.
This is the stool you want. Don't bother messing around with some cheap crappy version. This one is adjustable and built like a tank. Just get it.
