Is it recommended to upgrade Apple Watch Original to the updated software

Yes.

Yes. Absolutely. I've had no problems at all since upgrading mine. 3rd party apps and complications load and run much faster. It's a worthwhile upgrade.

Hi

In addition to the many new features offered by watchOS 3 (including significantly faster loading of up to 10 of your favourite apps), the update also includes important security updates.

In order to update your watch to watchOS 3, you will first need to update your iPhone to the latest version of iOS (which also includes new features and important updates):

• Update the iOS software on your iPhone, iPad, or iPod touch - Apple Support
• Update the software on your Apple Watch - Apple Support

More information:

http://www.apple.com/ios/ios-10/

http://www.apple.com/watchos/