We control the stuff that we installed... obviously.
If there's an apache upgrade or OS upgrade and such.. they usually notify us... and if we want them to do it, we just need to fill out a support ticket requesting it.
I'm not a "server tekkie". They take care of all I don't know how to do. I have lots of control (even root access) through the webmin panel. This has been useful when trying to install some stuff (like photopost/Imagemagic or neomail).
They can support other things... some for a fee and some is included. If you wanted them to tinker with threads... they would charge you. if it were PHP adjustments etc... they wouldn't.
Hope that help.
Let me know if you've got any other questions.
