Are RAID arrays proprietary to their controller? I am planning on changing motherboards, will I be able to simply plug the drives in and have the current array detected and working with no problems?
Depends....
They are proprietary to chip manufacturers and sometimes model.
Highpoint RAID chips generally play happy amonst themselves so you could take drives from one controller and connect them up to another and have them work without any significant changes.
Promise cards are touchy. If you go from one controller to another that's nearly identical (SATA to SATA/PATA combined) you're ok, otherwise it won't keep the array.
I don't know about Via's having limited experiance. Silicon Image's work fine amongst themselves.
If you're changing RAID controllers completely, like from Intel's southbridge to Nforce RAID, forget it. You're not going to be able to save the array no matter what you do. It's because each RAID controller chip handles RAID differently and writes to the drive structure differently. Back up your important and critical data and plan to do a complete install from the ground up.