Hi @endiz,
When you say “a seamless experience to the native ecobee & SmartThings integration”, do you mean through the “MarketSpace”?
This is a custom integration (just like My ecobee device), so you’d need to manually create the DTH and related smartapps and execute MyNextManager under MarketSpace>SmartApps>MyApps to connect your Nest devices to SmartThings.
This integation is based on the native ST UI, so rendering is faster. I hope that this post answers your questions. For more information about the custom integration flow, refer to
http://thingsthataresmart.wiki/index.php?title=My_NextServiceMgr#UI_and_integration_setup_workflow
Regards.