I've had the original Galaxy Gear since last year. When it was first released it used Android as it's operating system (And not Android Wear, that wasn't available at the time). Earlier this year Samsung decided to make Tizen the main operating system of it's watches. Tizen is an operating system derived from Samsung's Bada and some other efforts that Intel and others had underway.
The current climate in which it is being released is interesting. Google has released Android TV as their solution for the living room. Samsung and Apple have both released car solutions. Some televisions already suuort a series of applications for connecting to services, and the most dominant mobile operating systems are Android and iOS. In this environment Samsung is releasing an operating system to compete for market share across all of these fronts; the living room, car infotainment systems, portable mobile devices, set-top boxes, and more are the target device types that Tizen is aimed for. I might be pessimistic were it another company releasing a new operating system but I'm expecting better outcome from Samsung.
This week Samsung is releasing the Galaxy Gear S in the USA. This is the first Tizen devices with data connectivity. A few days later from the 11-13 November at the Moscone Conference Center (San Francisco) Samsung is hosting a developers conference covering Tizen and development for the Watch and the Tizen powered Televisions (among other topics, such as the SmartThings platform). I plan to be there. I've already started to look into Tizen and made my first Hello World program of types. The details of it can be viewed over at The Code Project.
From working with this first project and seeing the number of web standards that the HTML side of the development story is based on I can see it seems to be an easy platform to jump into. Those that have already been doing mobile application development with HTML will be able to start development with little effort compared to starting other platforms. Getting started is easy. Though some amount of additional effort will be needed when thinking of how tasks are divided between a phone application and a watch application; applications on the Gear S can run independently of the phone or in conjunction with an application on the phone.