I'm surprised that a lot of the comments seem to be missing the reason that this project exists.
In many tailwind projects, you inevitably end up wanting to standardize how a button looks, how a field looks, etc., rather than copy+paste the same 20+ tailwind classes that you need to implement a nice looking button in tailwind.
Can you just apply it to `button { @apply flex items-center blahblahblah; }` in app.css? Of course you can. Or you can use the btn from DaisyUI.
I think DaisyUI is just a shortcut for many common UI components that you will inevitably want to build out and that you will necessarily eventually standardize in any app that grows large enough.
How does it differ from bootstrap? Well, you can continue to use tailwind for everything else that DaisyUI has not implemented. It's just an additive layer to tailwind. The project is at its core just a shortcut for common UI components.
As a user, my criticism is that many of the DaisyUI components seem to be lacking good contrast, so some just don't seem to be usable. The theming situation is really interesting and quite cool to use, but if you look at the example page, it just feels hard to read. I can't really find a light and dark default theme that look good to me (re: contrast and brightness). I think the color hooks might just not be there but I didn't dig far enough in.
For me, I've found a lot of value in being able to easily copy+paste parts of DaisyUI source code, e.g., a particular widget and modifying it to fit my design system, rather than use it in its entirety.