Tips for migrating server/clients from suphp to fastcgi?

I am planning on using cloudlinux with a few of my new servers and with its overhead, id really like to minimize resource waste and optimize things as much as possible. FastCGI seems to be a bit faster than suphp and from what Ive been reading, people seem to prefer it.

Besides it being a pain for users to have custom php.ini's, what other gotchas are there for migrating users to it? Is there any type of howto or best practices for doing such a change? I migrated a server to it awhile back and i remember there were some issues that caused some sites not to work at all until changes were made, but I unfortunately didnt document the issues a the time.

Any advice is sincerely appreciated.