I first heard of Leonardo when I was searching for drawing apps to compliment the Surface Pro 3, and whilst I had primarily used PhotoShop, Autodesk and Krita with Wacom and XP-Pen tablets, I had heard great things about Leonardo.
*This is an updated overview of Leonardo, which is still available in Beta from Get Leonardo, and also now available on the Windows Store
It's been a year and 6 updates, and I still rate Leonardo as one of the best drawing applications available for Windows. Leonardo has a very intuitive work space, and being tailor made for Windows, it has a great partnership with the Ink Workspace bundled with Windows 10.
The beautiful and easy-to-use interface scales to any screen and is quick and easy to navigate, using either a mouse/keyboard or stylus devices. I always use a stylus, only using a keyboard when naming/saving work, and I have 'undo' and 'brush size' shortcuts mapped to the buttons on the pen. The latter works by holding the button down, and using the nib to increase or decrease the radius of the brush. Leonardo is also incredibly fast, starting in less than half a second, and makes it possible to paint with a large brush in really high resolution without lag.
As a digital artist, canvas sizing is a high priority, and especially in this regard, Leonardo's infinite canvas can be thought of as a giant sketchbook. Instead of turning the page just scroll in any direction and keep sketching. It's brilliant and is highly intuitive when working.
I've completed most of my commission pieces of the last year using Leonardo, an example being the Sonic the Hedgehog / Kingdom Hearts crossover piece below.
Everything from lines, inks, colours was created in Leonardo, only switching to Photoshop to add the "Chaos Hearts" text. It's an incredibly good application for artists using Windows, and whilst I'll always drop back into Photoshop for touch-ups or vector based work, Leonardo is where I'll start and finish all line / colour work.
Summary : Leonardo is an ongoing project, so it's growing in power and use with each update. For the moment, the 0.16.51 has provided a ton of stabilization upgrades, and features such as a Paint bucket and a Magic Wand tool.