This is post is now quite old and the the information it contains may be out of date or innacurate.
While recently migrating a client from a dedicated server which was proving a little too expensive over to one of the great value Linux Virtual Private Servers offered by Web Fusion, I found myself frustrated with the 2mb upload limit apparent in the control panel side of things.
So I went and edited the php.ini to allow for a more generous upload limit. Restarted the server but to no effect.
After a closer inspection I realised that the Plesk control panel actually had its own separate php.ini file. Edited this file and it works.
Another Problem Solved :–)