We have had a number of clients attempt to upgrade to PHP 5.1.4 as a result of this, and things didn't look too good afterwards

When downgrading to PHP 4.4.2, note that cPanel doesn't always seem to re-enable the mod_php4 module in the Apache configuration file (/usr/local/apache/conf/httpd.conf), and as a result you may need to edit this file to uncomment the relevant lines to fix things. If this happens, you'll know because all PHP files become downloadable, as they are no longer parsed.
It really would be good to see cPanel think about their releases in more detail. For a start, the message that appears in WHM is outdated, confusing and causes panic amongst clients. As system administrators, if we don't happen to login to WHM on a server very shortly after the "alert" appears, the first we know of it is when clients get in touch having broken their servers due to the bugs in the cPanel EasyApache system. It does seem that we spend a larger amount of time than should be necessary running around after cPanel attempting to resolve issues that really shouldn't have existed in the first place.
Craig.