OS X 10.11 El Capitan
El Capitan is a beta product -- though, in general, OS X is still the biggest commercial competitor to Windows. For the most part, it makes more sense if you already have or plan to buy other Apple products.
In comparison to the current release (Yosemite), El Capitan changes the system font to the San Francisco typeface used in the Apple Watch and the upcoming iOS 9. El Capitan also brings support for snapping two windows side-by-side, a feature other OSs have had for years.
Also new in this release is improved display support for Chinese and Japanese, and an improved Japanese IME (Input method editor). The IME allows the user to write in Japanese by typing phonetically (in Hiragana), and generates the correct Kanji without user intervention by using frequency and context-sensitive clues to determine the correct Kanji.
Killer feature: HiDPI ("Retina") display support is more mature than what's available with other OSs.
Price: Free upgrade, though using OS X requires Apple hardware, which starts at $499 for the Mac Mini.
Image: Apple Inc.
James Sanders is a staff technology writer for TechRepublic. He covers future technology, including quantum computing, AI/ML, and 5G, as well as cloud, security, open source, mobility, and the impact of globalization on the industry, with a focus on Asia.