I really like them, although they don't always have full HD. Google Chromecast is now a dongle that functions like a TV box.
As a general wee computer, I do like them. I also know how to make your phone a mini laptop with a hub. But many phones don't do screen mirroring with a cable, so you may have to do casting.
You can play games on them and they are not expensive at all. Thus, if you need a zero budget mini PC, they are fine.