I have a Mini 128GB. Last phone was an iPhone XS. I don't regret buying a Mini, but I don't know if I'd buy it again, either. I love how small it is. It's very light, fits easily in my pocket, and is generally a joy to use. Personally, I don't think it feels at all faster than my wife's XS, but I don't need it to be faster.
For me, the negatives are that it's hard on my eyes (I'm 40), and the battery life is shorter. The battery life isn't terrible. I knew I was going to get a smaller battery with this, and it's been reasonable, given its size. But if you're used to a Plus/Max phone or even the XR, this is going to seem like a crummy battery. I'm 40, so my eyes aren't what they used to be, and extended reading periods on the phone do cause my eyes to strain a bit. They don't strain when I use my wife's XS. But these are the tradeoffs. You can't have a tiny phone with the best battery life and biggest screen. I wish I could somehow travel around town with the Mini and look at an 12 Pro Max screen.