There has been some changes to the admin console from Server 8 to 9, and from 9 to 10. Server 10 has improvements on using multi-core processors as well as changes to way backup scehdules were done. Overall, there are significant changes but the admin console will be the biggest one.
With reading up on the WhitePapers and Tech Briefs priorhand, I dont think that you should have much trouble in the transition.
BTW, you have not stated what the hardware specs are on your machine.
Thank you mr_vodka, for your answer.
To be truthful, I do not have the specifics on the hardware but think that they use windows server 2003 and the clients access the FM server over remote desktop, the usual setup as the server is not inhouse.
These IT guys are supposed to be pros so I dont foresee any problems regarding the installation itself, I'm more concerned that my customers using FM Pro 9 clients might experience some hiccups.