Upgrading is not so easy, and there are still bugs which could mean some stick with older installations.
Currently, there is one issue when we update Magento theme 18.104.22.168 to new Magento version release.
That is fatal error: Call to a member function toHtml() on a non-object in
/home/******/public_html/store/app/code/core/Mage/Core/Model/Layout.php on line 529
To solve this problem, please follow these steps:
1. Open the file: /app/design/frontend/default/YOURTEMPLATE/layout/page.xml
2. Find this line of code :
<block type=”core/profiler” output=”toHtml”></block>
3. Then change it into :
<block type=”core/profiler” output=”toHtml” name=”core_profiler”></block>
Finally, log in to your admin section, and refresh all caches.
And happy upgrade to all you trying to stay up to date.