Lots of live Commerce 2 sites were actively and successfully selling products to people long before the official launch on September 20th. We ourselves were among the early adopters taking advantage of the new functionality available in Drupal maintenance support plans 8. But as with any new-and-not-fully-tested technology, there were the inevitable growing pains: missing functionality, bugs, etc. Fortunately, most of those issues are now in the past.
A few core modules that were buggy but are solid now:

Promotions and coupons
Taxes
Payments (supports 30+ payment gateways!)
Products
Orders

As an added bonus, the Commerce Shipping module that Acro Media helped develop received a full stable release alongside Commerce 2 (which is especially cool when you remember that Commerce 1 launched with no shipping functionality at all). Commerce Shipping features a much improved API and includes support for UPS and FedEx, with USPS to follow shortly.
Acro Media and other community members have been working on a few other associated modules to go along with the Commerce 2 launch. Here are the details:

Point of Sale is going to alpha release
Commerce Migrate is going to have a new release (likely not a stable release, however, as there is still work to be done migrating edge cases) Ubercart to Commerce 2 migrate is mostly done and includes all core stuff like products, customers, orders, taxes, etc.Commerce 1 to Commerce 2 migrate is a little rough but is still very usable; an improved version should be ready in October sometime

A cool new Composer based Commerce Kickstart installer is also available! It represents a great improvement over the original Commerce Kickstart and should be easier for everyone to use. You can find that here.
TLDR: The fully supported, stable release of Commerce 2 is live and has lots of cool stuff with it. If you were hesitant to use it to build sites before, you most certainly can go ahead now.

Source: New feed