I'd definitely upgrade some things. The extent depends on the size of the windfall. I've recently come off a multi year austerity, and I've got to tell you that it's nice to spend again. It feels a little weird, but also a bit of relief. I do like getting a few new clothes, and going on vacation, and not feeling terrible about spending money unnecessarily. I'd still probably keep my ultra cheap cell phone plan, because I don't feel like anything is lacking there at all. Still try to cook at home, as it's healthier.
So, I'd probably pursue a lifetime goal of designing and building my own house. I wouldn't mind a younger vehicle, as mine is a 2011. More better quality clothes for the kids. Quit my part-time job, as the early mornings are a drag for all of us, and it is interfering with summer learning opportunities for my kids. Lots more vacations. My DH would continue working for a few years if it were only $1M. We don't trust ACA continuing as a reasonable option for us.
For Powerball levels, multiple houses and maybe a medium boat. Start my own charity. Give to causes that I feel deserve it.