I've been using Dogwaffle casually for a couple of years now. When I want to have fun and doodle, it's my goto app. I especially recommend it for old-timers who miss DPaint, because many of it's tools are inspired by that classic app (even some of the hotkeys are the same. I was surprised I remembered them after all these years). Especially good is the ease in which you can make custom brushes. IMHO, it beats Painter in that regard.

There are negatives, however. Dogwaffle has layers, but only the bottom-most layer is "standard", or opaque. All other layers are merely modifiers, like "multiply" or "subtractive". Also, I wouldn't recommend Dogwaffle for print work. At print resolutions, Dogwaffle begins to bog down, and it doesn't support CYMK. Dogwaffle's internal brushes are fairly small (35x35pix), so using them with some features (like rotation) can cause aliasing problems.

But I don't want to discourage anyone from giving Dogwaffle a test-drive, because it's very fun to use.

If you need a simple paint program, you might also try OpenCanvas 4. It doesn't have all the features of Dogwaffle, but it's basic tools just feel "right"...y'know, "smooth".