What Version of Magento CE adopted Magento Connect 2.0?

Magento Connect Channel 2.0 support was introduced first time in CE 1.4.2.0-rc1. However, some problems arose and in rc2 it was replaced with MCC 1.0 version. It was introduced again in 1.5.0.0-alpha1 and from that time is used in all Magento releases. I believe this information is included into official Magento Connect guide.

Magento 1.5 and up require Magento Connect 2.0

According to this post if you package it for Magento Connect 1.0 it wil automatically create the 2.0 version for you. But then again, who wants to support Magento Community versions < 1.5 in 2013?

http://www.magentocommerce.com/wiki/7_-_magento_connect/packaging_a_magento_extension_in_1.5

Magento Version 1.4.2.0 installs the 1.5 version of the Community 2.0 installer.

Just did the intermediate upgrade to 1.4.2.0 to next move forward to 1.6.2.0 and having the ability to access all the needed 3rd party module upgrades in 1.4.2.0 that require Community 2.0 was a huge plus.

Remember, ./pear is replaced with ./mage after the upgrade to 1.4.2.0 if you're using the command line version.