How easy will upgrade CI from 2.1.x

I am using CI in my 5 live projects. How easy will upgrade CI from 2.1.x. I am very excited to update CI.

Any guide on this?

Check it here
http://www.codeigniter.com/userguide3/in...ading.html
http://www.codeigniter.com/userguide3/in...e_211.html

>>> I am using CI in my 5 live projects. How easy will upgrade CI from 2.1.x. I am very excited to update CI.

I have all the latest versions installed "above the root" in a ci2 folder and change a single line in index.php:

# index.php
#$system_path = 'system';
#$system_path = '../../ci2/CodeIgniter_2_1_4/system';
#$system_path = '../../ci2/CodeIgniter_2_2_stable/system';
$system_path = '../../ci2/CodeIgniter_2_2_0/system';



Also in a common footer I have the following:
echo '<span class="flr">Fuelled by: CodeIgniter - ver: ' .CI_VERSION .'</span>';